When making an angled cut across a sheet of plywood or OSB, such as for a valley or a gable-end wall, I used to drive a nail into the sheet, hook my chalkline to it, and then snap the angle. Often the sheet was not supported where the nail was being driven, though, resulting in the sheet bouncing around and making it difficult to drive in the nail. Now I have a new method. First, I mark the short and long points of the cut. Then I take out my rusty and nicked chisel that I carry for rough framing. At one of the pencil lines, I drive the chisel about 3⁄8 in. into the edge of the plywood at the approximate angle of the cutline. I place the string of the chalkline in the notch made by the chisel, letting the hook dangle underneath. When I pull the line tight, the hook snugs up to the under side of the notch, and I snap the line.
Tynan Eggler, Vancouver Island, B.C.