If you have a toolbox, you can mount yakima blockheads locking or non-locking right on the face of the box. I've got 2 on mine, with room for a third in the middle. If you go non-locking, grab a coated cable and lock one end on the truck bed (mine is on a tie down) and then have another lock to lock around the bikes after you run the cable through the frames. You can get the locking blockheads keyed alike. I can post pics if you want.