We do not currently know of any antonyms for pontil.
The noun pontil is defined as:
A punty; a metal rod used in the glassblowing process. After a glass vessel has been blown to approximate size and the bottom of the piece has been finalized, the rod, which is tipped with a wad of hot glass, is attached to the bottom of the vessel to hold it while the top is finalized. It often leaves an irregular or ring-shaped scar on the base when removed called the "pontil mark".
