Dick,

A word picture might be enough...

Six inch long, high quality* slim needlenose pliers, spring opened. A  finely machined drill hole, half in each jaw, located just the jaw side of the hinge. Ends of the hole are slightly and smoothly radiused.

Carl stresses that it takes numerous squeezes, with the "barrel" rotated slightly between each so you don't form a flat, or flat sided crimp. Easy to do a smooth, round-section crimped barrel of aluminum or copper tube, with a tiny, slightly raised 'rim' at each end. Part of the prep is to 'flare' the tube to remove interior burrs and create a slight radius. For Aluminum or copper, a twirl of a #11 blade does fine.

*- The hinge must be good enough to stay tightly aligned.

 He also makes two sizes.   The smaller one is for doing lines.