Lay the String Back Over the Hook to Snap an Angled Line Alone

The Problem

The hook on a chalk line box is a flat metal tab about an inch wide. Hook it over the edge of a sheet of plywood or fiber cement and the string doesn't start at the edge — it starts at the far side of the tab, roughly an inch in.

For a line parallel to that edge, the offset cancels out at both ends and the line lands where you want it. For an angled line it doesn't. An angled line has to pivot on one specific mark, and an inch of error at the pivot swings the far end of the line well off target. The usual workaround is a second person holding the string on the mark, or a foot, or a straightedge clamped down to hook against.

The Technique

1. Mark where the angled line starts.
2. Pull string out of the box and lay it back over the top of the hook, so the string wraps the hook body instead of running straight out from it.
3. Set the hook down with its center on your mark. The string now leaves from the middle of the hook rather than an inch past it.
4. Hold the hook there with one finger, walk the box to the other end of the cut, and pull the string taut to your second mark.
5. Snap.