Mounts brake bar to top of runners Mounts brake bar to top of runners. Typically 3" long with a 1/2" hole to accept the nylon bushings and hinge bolts. We usually do not drill the mounting holes for the runner in case you can utilize existing bolts through the runner for at least one of the mounting bolts. Specify the width of your runner, typically 1.25" 0r 1.5".