lock into
US /lɑːk ˈɪntuː/
UK /lɑːk ˈɪntuː/

1.
to commit oneself to a particular course of action or situation, often one that is difficult to change
:
•
We don't want to lock into a long-term contract without careful consideration.
•
Once you lock into this payment plan, it's hard to change.
2.
to become firmly fixed or engaged with something else, often mechanically
:
•
The gears need to lock into place for the machine to work properly.
•
The two pieces will lock into each other with a click.