seal

put (or set) the seal on put the finishing touch to.

seal of approval: seeapproval.

seal someone's fate: seefate.

set (or put) your seal to (or on) mark with your own distinctive character.

☞ The reference in both of these idioms is to the former practice of stamping your personal seal on a completed letter or other document.

signed, sealed, and delivered: seesign.

someone's lips are sealed: seelip.