Setting Valve Clearance using Vacuum Gauge

All I want to know is how did they keep the allen wrench (or box end on the lock nut depending) on the fastener while it's bobbing up and down? Stud rockers are easy... the adjuster doesnt move while the rocker does. On a mopar.. no way. Maybe he's driving a magnum? I dont know. Never mind the mess... my hands would be trashed...