Need help with term/ name of a tool "impact cap"

I know EXACTLY what you mean, but couldn't find a reference to it in my old Briggs manuals- but maybe this will help:
Briggs WMB Gas Engine Motor Flywheel Removal Tool Knocker Models N U W 5 6 8 | eBay

Actually LOL that looks like a lug nut!!!. But thanks for the reference that is certainly "the idea"
"Flywheel knocker" sees to have "released the flood gates"

flywheel knocker tool - Google Search