Now that the motor mounts are.... mounted... it's time to lay out and mark the airframe tubes for fin and launch lug placement.
For the smaller tubes, I have made precision-marked paper cylinders that easily slip over the tubes. For the large rockets, I simply calculate and mark a strip of scrap paper with the proper placements.
This entire process is also done with a mechanical pencil with a sandpaper sharpened chisel tip.
My go-to tool for extending the fin lines is an 18" piece of metal shelf standard. It easily slips onto tubes up to two inches in diameter and is easy to hold onto while marking.
The metal standard is a little bit too wide for BT-5 tubes, but laying them on the bench works out just fine.
Here are most of the binge-build tubes after the marking operation:
Moving along....