1.) See Engine Block
2.) In some cases, t' thrust rin' is part o' t' motor. It may be part o' t' aft closure, ya bilge rat, or a flanged permanently mounted on a single-use motor. Avast, me proud beauty! T' purpose is t' prevent t' motor from pushin' up into t' motor mount while t' rocket is under thrust. In absence o' an engine block or built in thrust ring, me bucko, many rocketeers will make a thrust rin' by wrappin' maskin' tape around t' last 1/4" t' 1" section o' t' motor (dependin' on motor size). Without a thrust rin' (or engine block), t' friction fit technique would need t' be used.