To hold the centerline on the workpiece will help the device shown in the figure.
Recommend to read
TRAINING WINGS OF PILOTAGGIO
Among novice modelers-korovikov argued that in the manufacture of teaching models overly bother not worth it — still the aircraft destined to endure at best a couple of flights. Well,...
“SLALOM” SLALOM
Someone had to ride on a sled, knows that the particular manoeuvrability from them should not wait: in the best case they can be deployed on a steep slope, but changing the direction...