How to Truss a Pork Tenderloin? There’s many ways to do this and this is how Gary House from Cooking-Outdoors.com do.
Step 1: Assuming that you’ve stepped your pork tenderloin already, roll it up, leaving the same side facing down.
Step 2: Grab yourself a couple feet of cotton string or twine, starting at one end of the pork tenderloin. Slide your string underneath and tie a square knot. I like to tie mine three times on the bottom, this keeps the twine from slipping.
Step 3: Finish your square knot and then take several inches of twine, make a loop with about a quarter twist, slide that under your pork tenderloin about two inches from the first one and then snug that up by adjusting the twine.
Step 4: When you have that in place, make another loop slide that up a couple inches and repeat continue to do this until you reach the other end at which point you may have to flip it around and slide your loop over the other end.
When it’s finally all tied up, put a knot in it, snip off the loose ends, and you have a trust pork tenderloin.