DIY Network

How to Make a Lap Joint

When there's a piece of lumber that's too short for the project, a second piece of wood can be used to extend the length. Lap joining involves cutting two work pieces so one piece laps over the other.

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securing the joint
  • Time

    1 hour

  • Price Range

    $1 - $50

  • Difficulty



Step 1: Trace the Lap

Using a pencil, trace the lap on each piece of wood. The lap should be half the thickness of the wood and two to four times as long as the wood is thick. It's essential to measure so that the laps on both pieces of wood have identical dimensions.

Step 2: Set the Table-Saw Blade

Set a table-saw blade at exactly half the thickness of the first strip of wood. In this case, the pieces of wood are 2" x 4" lumber, whose thickness is actually 1-1/2", so the saw blade is set at a height of 3/4".

adjust height of table saw blade

Step 3: Cut the Wood, and Create an L Shape

Pass the wood through the blade, starting at the innermost edge of the lap (Image 1). Make as many passes as needed, working the blade toward the end of the work piece. Eventually you'll create an L shape in the wood (Image 2).

Step 4: Repeat and Secure the Joint

Repeat steps 3 and 4 for the second piece of wood. The two laps should be a perfect fit. Fasten the joint with glue. Secure the joint with wood screws.

fasten joint with glue and secure with wood screws