This newer version of the Hammer - with a curved black back brace - has sliding pins behind the brace that secure the brace to the car carpet. The older, black T-mount doesn't have these pins, and you have to either screw the mount somewhere (e.g. screw according to the instructions) or something with velcro or double-sided tape (e.g. ). Buy the one pictured with the curved bracket; You have other options.