Pelago, I used Senich's book that Jim Gaynor speaks of above. It has several good pictures that give a good look at how the handguard looks after the modification. I used a band saw and used double stick tape to attach the handguard to the side of a square piece of wood. I didn't worry too much about exact dimensions, just made it look like the picture. Some of these handguards were made in the field and I felt (have no evidence) there were no exact specs for this part. I've seen pictures of handguards that look pretty rough, particularly the cut out for the scope block.