The supplied frame insert tubes must be cut to the proper length. Determine the length by inserting a screwdriver through the first set of holes until it bottoms against the inner side of the framerail. Some cars will have extra pieces of sheetmetal inside the rail. If any of the insert tubes contact one of these pieces, be sure to measure the more shallow depth for proper fitment of the frame inserts. Record the depth by marking the screwdriver as shown (making sure to use the outside edge of the framerail), then transfer the measurement to the appropriate tube.