I often find it necessary to install joist hangers before installing joists. Working alone, I always struggled as I tried to hold the hanger in the correct position while nailing. So I came up with the simple fixture shown in the drawing to give me another hand. The fixture consists of a short scrap of one of the joists I’m installing, with a strip of 3/4-in. plywood screwed to its top. A twist strap nailed to the bottom of the fixture tightly holds a joist hanger against the bottom edge of the scrap (a little creative bending of the twist strap creates a spring-clamp effect).
To use the fixture, I place the overhanging portion of the plywood scrap on a layout mark on the beam. Then I temporarily stake it to the beam with an awl driven through a 1/4-in.-dia. hole in the end of the strip.
—Jeff C. Johnson, Glen Allen, VA
Edited and illustrated by Charles Miller
From Fine Homebuilding #185