A window T-lock is a type of locking mechanism for windows that consists of a T-shaped metal lever that rotates to lock or unlock the window. The T-lock is typically installed on the window sash and engages with a corresponding catch on the window frame to secure the window closed. This type of lock is commonly used on casement windows and can be found in both keyed and non-keyed varieties. The T-lock provides a simple and effective way to secure windows against intrusion.