You'll note that there is a mounting template printed on the top flap of the carton your reel came in (or you can print it off here). You can use this to mark your hole position when you mount your reel. Please note that you must support the bottom mounting boss of the reel in the bottom bracket as you are attaching the top bracket. If you don't support the reel and leave it hanging at an angle, undue stress is placed on the mounting boss which can cause the mounting boss to fail immediately, or soon after use. Refer to your manual for the various positions your reel can be mounted in as well as recommended heights for mounting.