lock in

To secure (someone or something) in a locked enclosure.

To fix the value of something potentially variable.

“I've locked in a rate of 5%.”

A sleepover party, usually held in a public place such as a church or school, in which the participants are not allowed to leave until the next morning.

“The youth group will have their annual lock-in this weekend.”

An illegal but widely-tolerated invitation-only gathering in a British pub, after the end of licensing hours, to allow regular customers the opportunity to enjoy further drinking time.

A situation in which members of an industry have agreed to adopt a certain standard and have retooled their production to meet this standard, thus making it very costly to change to a different standard.