heres what the site said
"Here it comes the heads: despite the name, T-Rex, the jaws of this vice are made to work with great delicacy to fix the hook in two points without requiring too much pressure. Therefore you can finally use every kind of salmon fly hooks with no chance of damaging them. Antique hooks, new hooks made by the best makers, home made or reshaped hooks, no matter if japanned of painted, they will be safe and protected by the double touch of this vice.
Combined with a thin piece of paper or plastic, for the usual additional protection, the two points pressure give optimal fixing strength with a light touch.
When used with normal fishing flies, for bass, pike, saltwater and salmon, we can tighten the jaws even stronger giving a bomb proof fixing to the hooks."