you can do it the old fashioned way of gluing sand paper to the correct size spar material and then sanding till flush.i use a square cutting bit in a router on a raouter table or using a hollow ground blade in my table saw raised to the proper depth for 1/8"wide slots,swicthing to a dado cutting blade for wider cuts.these are all inexpensive craftsman desktop tools bought used over a 20 year period.