Published in The Strad magazine, September 2018 - page 90 “Trade Secrets"
 

“Shirley White Demonstrates How She Built and Uses a Jig She Developed for the Correction of Deformed Plate Archings"

By securing the top  of an instrument to the bottom layer of the jig, a second layer is added allowing one to
GENTLY push the arching from both sides, moving it back into shape slowly over a period of time.