I often find it easier, especially doing built-in units on site, to bring some hand-held power tools to the lumber and plywood pile rather than hauling the material back to the shop. I use a circular saw to make my cuts, and with the help of a kerf block, 1 can make the cuts quickly with accuracy that's around plus or minus 1/16 in. What's a kerf block? Read on.
First, I set the depth of cut on my circular saw. Once it's set, I don't change it, or I'll have to make another kerf block. Next, I grab a scrap piece of wood. A 1-ft. long piece of 1x4 is good for this process. Now, using my square, I start cutting across the block. I stop the cut midway, and with the saw stuck in the wood, I use a sharp pencil to mark the edges of the saw's table on both sides of the cut. The block should look like the one in the drawing.
Now when I want to make a cut in a sheet of plywood, I mark the dimension on the plywood and hold the block on the work so that the kerf lines up with the mark. Then I note the edge of the saw table (whichever side is most convenient) with a pencil mark on the plywood. I use these marks to position a clamped-on straightedge to guide my circular saw. This method works equally well when dadoing with a router.Randall C. Smith, Barrington, NH