Review on Camera Mount Tripod Screw Adapter by Scott Gafur

They are excellent for inserting into profile 4040 with T-slot for mounting flash units, digital SLR cameras etc. on a common rail. The flat bolt enters the T-slot with a slight incline and you can slide the bottom nut down toward the extrusion to lock it. The second thumbscrew can then be tightened on the camera to secure it to the rail. If you're ordering a 4040 T-Nut you might want to see if it has a 4040 light mode when you mount it on a tripod. When using this to create a photo booth from Profile 4040, the standard profile is great for attaching flashes and accessories. It has a bit of play in the slot, but for a cheap option it works amazingly.