Chef’s knife preferably
Place your knife blade just under the fat and with the knife blade sideways or basically parallel to the cutting board, cut off just the fat with a back and forth sawing motion. There is usually a white membrane on the pork as well. Place your knife blade just under the white membrane and with the knife blade basically parallel to the cutting board, cut off just the membrane. Once you have a small piece of the membrane cut, with your other hand, hold the loose piece parallel to the cutting board and continue cutting until you have all of the membrane cut off. You will cut off a little of meat as well, but that’s ok. If you only cut off part of the membrane, just follow the same procedure and cut off each piece of fat and membrane.
I use this method to trim a pork tenderloin for my California Grill's Grilled Pork Tenderloin Recipe.