To apply painter’s tape in corners, start by running the first piece of tape along the baseboard of the wall, through the corner, and up the perpendicular wall. Burnish the tape firmly with a putty knife, then cut along the crease with a sharp utility knife, thus removing the excess tape from the wall. Repeat this process with the adjacent wall, starting about a half-inch away from the corner of the other wall, in order to keep your first tapeline sharp.