# 9.2: Using CLTV in Scripts

> **NOTE:** This is a draft in progress, so that I can get some feedback from early reviewers. It is not yet ready for learning.

`OP_CHECKLOCKTIMEVERIFY` (or CLTV) is the natural complement to `nLockTime`. It moves the idea of locking transactions by an absolute time or blockheight into the realm of opcodes, allowing for the locking of individual UTXOs.