Actually you can do it without a whack or hammer at all.
Take two tenderloins of almost equal size.
Trim to length.
in the middle of each tenderloin, slice almost through.
then slice each half the same way so you have from 4 to 6 cuts depending on size.
open them up well. both tenderloins. Brush with a mixture of butter and bacon grease.
Place stuffing on one half level to the cuts plus 1/4 inch above the cuts
place the 2nd tenderloin on the first.
Tie with twine. One wrap per 1.5"inches (3.25 cm)
roast 375 with an apple jelly glaze
I've had great success with these using stove top stuffing with 3/4 cup of apple sauce! Fruit stuffings work great with this. Next time I do one I'll post it, if I ever remember how to get pics up in here.