On straightforward roofs with rectangular shapes, snapping chalklines on the sheathing is easy because chalkline hooks are designed to grab at 90°. When a roof becomes more complicated, with hexagonal or octagonal shapes, it is tougher to snap the cutlines. The chalkline’s hook just can’t get a good grip on the edge of the sheathing. With the device shown in the drawing, snapping angled lines is a breeze.
Made from a short piece of aluminum-angle stock, the top of my chalkline anchor has a screw threaded into a hole drilled and tapped into the angle stock. The chalkline’s hook fits over this screw. A cutout in the top of the anchor lets me easily see the dimension marked on the sheathing’s edge as I position the anchor.
Once the anchor is in position, I push on its side, setting two dog points into the edge of the plywood. The dog points are simply sharpened screws held in place by a pair of nuts. The thickness of the nut between the anchor and the plywood serves to center the top screw directly over the dimension mark.
Bob Carli, Unionville, CT
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