Match the correct-sized bending die with the tubing. The tubing will have sizing marks on it or the package it came in. The bending dies use marks near the pivot point to identify its size and a row of angle marks along the curved edge of the bending die's channel.
Mark the tubing at the place where the bend starts with a pencil.
Open the tubing bender's handles fully. Near the hinge, one handle holds the stationary clamp and one holds the pressure die. The bending die connects to the handles hinge.
Place the marked tubing on the bending die's channel with the starting mark facing the stationary clamp and the bend area facing the bending and pressure dies.
Slide the tubing along the bending die and into the clamp until the pencil mark on the tubing lines up with the bending die side of the clamp. The clamp, often found on the stationary handle, usually uses a stationary bar but sometimes uses a fold-over style clamp.
Close the pressure die's handle until the tubing receives tension from the clamp, bending die and the pressure die. Verify the tubing squarely sits in each die and the 0-degree angle mark on the bending die lines up with the arrow found on the pressure die. The pressure die's arrow measures the bend angle.
Close the handles with firm steady pressure. Keep an eye on the arrow. When the arrow reaches the desired bend angle stop closing the handles.
Open the tubing bender's handles, release the clamp and remove the tubing.