Checking for "square"
To check a square for "square" draw a line across the plywood using the edge to be checked. Flip the square to the other side of the plywood and draw another line close to the first and see if they are parallel. If not, it's one of two things: the edges of the plywood aren't parallel (not likely) or the square is not "square". Adjust the square to 1/2 the distance "off" and try again. Generally speaking aside from bargain sheets, the plywood is close enough to square for the jobs I do. A drywall square can also be used as a reference since it's got a 48" long leg.
I also use a ball point pen when doing layouts since it makes a fine, but dark line for accuracy.:thumbsup: bill
To check a square for "square" draw a line across the plywood using the edge to be checked. Flip the square to the other side of the plywood and draw another line close to the first and see if they are parallel. If not, it's one of two things: the edges of the plywood aren't parallel (not likely) or the square is not "square". Adjust the square to 1/2 the distance "off" and try again. Generally speaking aside from bargain sheets, the plywood is close enough to square for the jobs I do. A drywall square can also be used as a reference since it's got a 48" long leg.
I also use a ball point pen when doing layouts since it makes a fine, but dark line for accuracy.:thumbsup: bill