When mounting the VAAST Vertical Mounting Bracket its best to locate close to the edge of the rack so the Tap Cap is easily accessible, as shown below. 

The bracket is designed to mount to standard platform racks like Rhino Rack. If you are using the Front Runner platform rack with a raised edge, cross bar racks or mesh racks we suggest using the VAAST Bracket Adapter Mounts (VST01-A005).