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    Lap Joint Basics

    Aside from the basic butt joint, which isn’t really a joint at all, the lap joint is your simplest option for joining pieces to make a frame of some kind. It is simply a notch cut out of one board, and a similar notch cut out of another. Then the two pieces are overlapped (hence the name) and glued together. Because there is a big surface for the glue to grab, the joint is actually pretty strong, but you have to make sure to clamp the notches together very firmly during assembly. Because half of each piece is removed to create the joint, it is also called a half-lap.

    There are two basic types of lap joints, one at a corner and one where two pieces cross each other. Both can be cut in a bunch of ways. You can use a dado set or a tenoning jig on the tablesaw, you can rout them with a straight bit, or you can cut them with hand tools: saw and chisel.

    The most common way this joint is used is to make gridwork, such as muntins, those thin, crisscrossing pieces that divide windows. It’s hard to cut a more complicated joint on these skinny pieces, and lap joints are plenty strong for the job. But you can also use lap joints to make door frames and small boxes, too.

    Basic Lap Joints

    A lap joint is just two mating notches, one of the simplest joints there is. But if you apply glue and clamp the surfaces together very tightly, it is also very strong.
    The window muntins on this small cabinet door meet at a cross-lap joint.
    Lap joints can even be used to make small boxes like this one from Gary Rogowski. Note how he added brass nails for a bit of extra strength and decoration.
    Lap joints are simply notches, so you can cut them with any number of tools. The simplest way is with a handsaw.
    You can use a chisel to fine-tune the notch.
    The glue-up is always complicated with lap joints, because you have to squeeze them together in every direction. Do a dry run first, with no glue, to make sure all your clamps are in order.