I think you are referring to the phase of a build where you are cutting the part of the butt where the buttplate goes.
I never have found it necessary to use tape. I cut the curve with a fine pitch frame saw and then use rasps and scrapers for final fitting. Fitting a butt plate takes time and patience. In all of my builds the blank has been sufficiently thick that if there was any chip out it would be irrelevant once the butt was shaped down to the buttplate profile. Notice though that when I am installing the butt plate the final shaping of the butt has NOT been completed. The buttplate goes on right after the trigger is installed.
(The barrel locates the vent, the vent locates the lock, the lock locates the trigger and the trigger locates the buttplate in my building sequence.) Even on a pre-carved stock I think that a fine pitch saw and slow cutting is a more prudent approach than any method that would require tape to control chip-out.
Best Regards,
JMC
Best