Originally Posted by
taguy4
A fourth hand tool, or a 3rd hand tool? A 4th hand tool just pulls the cable tight whereas a 3rd hand tool holds the brake calipers (or cantilevers) up against the rim. If you would use a 3rd hand tool to hold the cantilevers while you slid the long brake pads under the fork blades/set stays to install them, you would have to find a tool with just the right amount of tension to hold the cantilevers far enough away from the rims to allow the brake pads to be installed, unless I'm missing something.
With the wheel off, I put the pads on the arms and finger-tighten the bolts. Then I put the wheel on and use a fourth hand tool to tension the cable enough to hold the pads against the rim while aligning and tightening them. See video at 0:56 below: