Join Date: Jul 2008
Location: Dickinson, Tx. / Somerville, TX
As said earlier, lay the short edge along a shelf and draw a line up the long edge. Now flip the short edge over in the opposite direction and lay it up against the line drawn They should match perfectly - the edge of the square should be laying right on top of the line you drew.
You could spend the extra bucks and get an Engineers Square. They should be right on right out of the box. Like I said once before: Think of Lowes as Walmart and Home Depot as K-mart.
here is another mind blower. I havent tried this is a few years but here goes. Pick up two or more tape measures and lay the hook ends on a table top. Pull out the tapes about 3 feet or so and look at the differences all along the way.
Anyway, back to squares. Go to a store that sells drafting supplies and buy the plastic triangles. they are cheap and very accurate. Only down side is that they dont come with a secondary edge to lay against anything. They are totally flat. You have to just lay one edge on there by sight and feel which is not a big issue. If you want to use it as a typical square, surely you can find a straight piece of wood, drill a few holes in the plastic square and into the wood to create an outside edge to lay against your work piece.
One would think that in this day and age of technology that some manufacturers can make a square that is actually square and for a reasonable price.
Retired woodworker, amongst other things, Sold full time cruising boat and now full time cruising in RV. Currently in Somerville, Tx