tighten, tie, shut, lock, fasten
締 centers on pulling something closed so it stays secure: tightening a knot, tying a string, shutting a door, locking a container, or fastening a belt. All its meanings share the idea of making something firm and closed by applying tension.
締 combines 糸 (thread) with 帝, which likely contributes the sound テイ and the idea of binding or tying tightly. The thread radical reinforces the action of fastening with cord or string.
The left side is thread 糸, and the right side 帝 looks like a crown or a tight cap. Imagine pulling a thread tightly around a crown to fasten it in place: 締 means to tighten, tie, or lock something securely.
For テイ, picture a tailor tightening a thread around a hem and saying 'Tight!' with a slight accent: 'Tayt!' The sound 'Tayt' cues テイ while the thread 糸 pulls everything tight.
company director; board member
to tie; to fasten; to tighten
conclusion; execution (of a contract); entering (into treaty)
deadline; closing; cut-off
tying up; binding; fastening; tightening
control; management; supervision
pressure; clamping; tightening; fastening
tightening
to manage; to control; to supervise; to oversee; to command
closing (properly); shutting
manager; controller; administrator
shutout; shutting out; lock-out; freeze-out
conclusion; end; finish; settlement; summary; summing up; rounding off
to bring to a finish
conclusion of a treaty
to become tense; to be tightened; to become firm (e.g. body)
to tighten; to stiffen; to brace; to strain
to tighten; to fasten tight; to constrict; to compress
locking up (doors and windows); fastening the doors
to shut out; to bar; to lock out; to exclude