To avoid losing a ball of string when you’re walking a plate, laying out a hillside or stringing a ridge, wrap your line around a butterfly spool. You can cut one out of plywood, or nail a couple of short pieces of lath together. To play out the line, hold the string instead of the spool. The butterfly will unwrap in jerks and jiggles, never getting too far away from you. If it does happen to wander, just give it a jerk and it will fly right back to you.
Robert Rix, Arlington, VA