The Red Box nail on has knockouts for ½” fittings and romex. It has a holder for the EZ-Brace 101. Angles are cut to accommodate the EZ-101 with a fixture canopy, or simple light fixture. Knockouts are for the Channel brace bar which gets supported to the Red Box by a 6-32 machine screw. The brace bar can be used with ceiling joist at 16” on center or less.