Skip trowel is a technique of applying drywall mud to a wall with texture. It is a technique that may take some time and practice to develop. Be prepared to be frustrated but if you stick with it, it is a rewarding skill to have. In order to skip trowel, you must load up a small line of mud on the edge of your trowel and drag that mud at an angle with the right pressure that allows the trowel to 'skip' resulting in texture on the wall.