There are several places you have to drill on avionics shelf and bulkhead under the seat. I used a right angle drill and step bit. When drilling these holes I took a piece of three quarter inch PVC pipe about four inches long and allowed the bit to go in the opening of the pipe on the oppissite side of each hole you drill and not into the brake lines or wire bundles. The brake lines and wire bundles are very close to where you will be drilling. Hope this prevents a wire nik or a hole in the brake line, it worked well for us.