How To Join Two Boards Lengthwise

March 7, 2022

Joining long wood boards side by side.

As a woodworker, you will encounter projects that would require you to join lengthwise two board pieces. If you’re just a beginner, you may end up scratching your head, figuring out how you would accomplish such a task. Of course, joining two boards lengthwise require more than gluing them together. You’ll likewise need to ensure that you reinforce the joints to make them sturdy and durable. 

When joining two boards lengthwise, you will utilize the board’s long grain edge and not the end grain. Moreover, when joining long-grain lengthwise to long grain, you would usually use a biscuit joint or glue the board together. Besides, as you become more adept in joining wood, you will also encounter concepts like tongue and groove and Mortise and Tenon joint.

Different Methods for Joining Two Boards Lengthwise

When joining two boards lengthwise, you will either need to add reinforcements or cut the joint in such a way that they produce mechanical strength for a stronger bond. The following methods for joining boards lengthwise will help you familiarize yourself with these methods:

Using dowel to joint 2 long boards.

1) Dowel Joint

When attaching boards using drill and dowel, you need to ensure that the hole depth is about half the dowel’s length, with a little extra for gluing. If you are using a jig, you should also account for that. The jig will keep your bit in the proper position, squared to the board during the drilling process. 

If you’re not using a dowel jig, the dowel will be handy. You will need to drill holes on the board. Then, place the center of the dowel in the hole. Afterward, you should align the panels as you press them together. 

The dowel center leaves a mark on the opposite board at the right spot where you will need to drill. Dry fit the panels using the dowels first to ensure that everything lines up well. 

Once you are confident that the pieces are rightly fitting, you can apply the glue to the dowels’ ends. Then, insert the dowels into the holes. You should also apply glue along the joint’s entire length of the second board.

Learn More About Dowel Joints.

use biscuit joints to joint wood boards together.

2) Biscuit Joint

Biscuit joints are so named because they use biscuit slots and biscuit-like plate jointer to join boards or woods. The lumber that you should join at the onset should have the same thickness. Then, edge and size the woods or panels to make them fit snugly together along the edges. Afterward, mark the biscuits’ locations where you would glue the boards. 

The distance between the biscuits will generally determine the strength of the finished plank. Moreover, you need to set the plate jointer’s cutting depth. If you only do single row biscuits, you will only need to position the joints at the board’s edge’s center. Then, cut the biscuit slots. Ensure that you secure the lumber or hold it tightly to push the blade into the lumber. 

Afterward, clean the biscuit slots to do away with debris or sawdust. Then, fill the spaces with glue about one-fourth full and spread glue along the board’s edge. Fit the boards together while making sure that they are adequately aligned. Sand down or plane them down when the glue has dried completely.

Read more about Biscuit Joinery Techniques.

Tabletop half lap joints.

3) Hap-lap Joints

Hap-lap joints belong to the most basic woodworking joints. You can use this joint when you want to join two pieces of wood of the same thickness. To do a half-lap joint, remove half of the wood material to fit together two boards. The half-lap joint is perfect for joining at a right angle, making the panels fit seamlessly. 

You can use the half-lap joints to join two-inch thick wood like the carcasses for any furniture piece. It adds sturdiness and strength to the furniture’s internal structure without adding height. When used correctly, this type of joint can be very firm. 

You can use various tools to make half-lap joints. But I usually use a radial arm saw with a stacked dado set. If you don’t own a radial arm saw, you can use a table saw along with a stacked dado set, though this option is more complicated than using a radial arm saw. Use your miter gauge for guiding the stock along the blade. 

You can likewise use a circular saw to make a half-lap joint. You only need to set the depth of the circular saw’s cut. Then, clean the remaining thin pieces using a chisel. 

When assembling, use some glue on one of the surfaces of the two matings. Then, place the other stock in place. Adjust the two until you get the final position. Then, using a few wood screws, hold the joint until the glue dries up.

Read more about lap Joint.

Tabled locking lap joints.

4) Tabled Lap Joints

The tabled lap joints use the strength and sturdiness of interconnecting parts along with the glued large surface of the half-lap joint. To achieve a tabled lap joint, you only need to add one-fourth-inch width to the workpiece. Then, measure the distance from the workpiece end. Afterward, you need to mark both stocks like what you would do in a half-lap joint. But before cutting, do a test cut to ensure the right thickness of your workpieces. 

As you would do in a half-lap joint, use a dado setup, though you need to set the blade’s height to 1/3 of the workpieces’ thickness. Afterward, rabbet both parts. Then, reset the height of the dado blade to two-thirds of the workpieces’ thickness. Test the height using a scrap piece of wood. Make sure both pieces’ faces are flush. 

Afterward, measure the dado’s shoulder to a distance of about one-half of the workpiece’s width. Then, mark the length. As you clamp both pieces against the miter gauge, do two passes to determine and define the second pair of dadoes’ width. Then, you can cut the dadoes. 

To make sure that you create a tight joint, you should trim each piece’s end slowly until both ends suit the deeper dadoes. Then, you can glue and clamp the workpieces until the glue dries.

Pocket hole joints on table top boards.

5) Pocket-hole Screw Joint

The pocket-hole screw joint is a quick solution to your jointing projects. With this joint, you can join two boards quickly and easily. Yet, before you can do a pocket-hole screw joint, you need to ensure that you have a pocket hole jig. With this jig, you can drill on your workpieces an angled hole. 

A high-quality pocket hole jig will make connecting wood pieces a breeze while helping you hide the screws to get a professional-looking work. Once you’ve drilled those holes, you only need to insert a screw to keep the pieces together.

Read more about pocket-hole screw joinery techniques.

Board Scarf Joint

6) Bevel-cut Scarf Joints

This is the most difficult joinery method for joining the wood lengthwise. And it’s very seldom been used in this kind of project.

If you will cut ends at a certain angle before joining them, you can expose long-grain better for a sturdier bond. If you have a sharper angle, you also get a larger surface for gluing. For example, if your angle is 45° bevel, you also increase the gluing surface by forty percent. This cut will also enable you to hide the joint line on the surface. 

First, you need to find a location where you will make your scarf joint. Then, mark the cut line and the seam cutting line. Afterward, make the scarf joint’s first half with a 45° bevel cut. Nail this piece to the wall. Then, make the second cut. 

Fit the second molding strip’s end into its corner, and mark the cut’s location. Make several cuts until you get the perfect fit. Afterward, drill pilot holes where you will nail the molding to the wall. Then, drive the nails and sand. Apply glue to the joint’s both ends and sand the joint smoothly as you touch it up with paint.

Frequently Asked Questions about Wood Joints

Aside from knowing the different methods that you can use to join boards lengthwise, you also need to be familiar with the FAQs about the wood joint because these questions might be the very questions that are playing in your mind:

How Can I Make Seamless Wood Joints?

Making a wood joint disappear or appear to be seamless is not an easy thing to achieve. You need to know the tricks on how to do it. First, it is easy to make the joint appear seamless if you use wood from the same cut-off logs. You should also carefully choose the boards that you would join together. 

Look for the best match in grain texture and color at the point where you would join. Making the joint look seamless will become more complicated if the boards come from different parts of the tree, for the grain and color may be different.

It will also be more complicated if the two boards come from two different trees, even if their species are identical. So, as much as possible, you should use stocks from the same tree, and the boards to be joined should have almost the same texture and color. 

If you are desirous of success when joining boards, you can purchase boards from Home Depot and Lowe’s because the boards they sell are very generic. The wood or boards they also sell usually come from tree farms that do not let their trees grow to the point that they develop unique features in their grain. Moreover, it will be helpful to know that wood with more character will be more problematic when you join them with other wood types.

To make your joint to appear more seamless, you need to ensure that the joint transition from board to board is as clean as possible. Once you are done with gluing and clamping, let the wood cure before you paint or varnish them. You can also make use of a damp cloth to wipe the excess glue away. In this way, you can keep the grain portion clean and easy to work with. 

If you see bent or curled part of the wood, most probably, the joined wood’s edges didn’t sit flush. You can use CNC Mill or a circular disc sander to do the trick in such a case. You can also straighten the jointed wood or boards by using clamps, bracing, or by merely letting time to straighten it back.

Should You Only Glue Wood Boards?

Gluing two wood boards may not be enough to make a sturdy joint. Yet, it is a case-to-case basis, depending on whether it can sustain the load over time. However, gluing alone may not be enough to support the joint over time. 

If you are joining wood for art purposes, the joint will never be used for bolstering a load. Thus, gluing them may be enough to sustain a joint. However, if you are joining two boards for supporting a substantial load over time, gluing alone may not suffice. 

Eventually, you will have problems along the way. In such a case, you may employ a biscuit joint to ensure that the joint will last in bare minimum. And you can use the wood panel clamping system to clamp multiple wood board panels at once for more effective glueing result.


Joinery is an essential aspect of woodworking, and in many woodworking projects, you will be required to join boards or stocks. So, if you want to take your woodworking skills to the next level, you need to be cognizant of the different types of joineries and the various methods and techniques to achieve them. 

You also need to consider the properties of the wood you need to join, like their strength, grain, color, and dimensional stability. Knowing these properties and applying the right wood-joining techniques will enable you to achieve great results for your woodworking projects.

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