What is it used for?

The ProTrim Knife is used to trim your backing paper along the back edge of the frame.

How do I use the protrim knife?

After sliding the blade in place (and securing it with the nut) line the knife along the edge of the frame using the edge guide. Place pressure on the blade through the paper and drag.  This will remove excess paper and help make the backing paper look clean.

Note: the blades used in the knife are sharp.  You can pierce your skin and cut yourself or someone else.