It's a little difficult to describe but easy to see. Portions of the Halloween costume below where foam-core meets PVC on the chest harness were attached using this homemade clip. This costume build and some other PVC mechanisms including a rotating hinge and linear joint is described in creatrope.com's general grievous costume.
To make a clip you need you the thin-wall version of the PVC tube. There's a thick-wall and thin-wall version - the thick will is usually my base for 'structural' elements, but the thin-wall makes a nice clip and is lighter.
Step 1: Cut Piece of Thin-Wall PVC, Align in PVC Cutters
Holding it vertically (and carefully) in the tube cutter rest the blade against the tube. This isn't how a tube cutter was designed to be use so work slowly and carefully, it's easy to slice a finger.
Make sure the cuts are straight vertical.
You'll make two cuts, about 120 degrees (1/3) of the tube circumference apart.
This produces one cllp (throw away the remaining 1/3).