This is making a lock very hard to open. There are all sorts of reasons why an adventurer might want to do this; I thought of it in the context of a time bomb in an artillery magazine. Glue is an obvious means, but may not stick to the oily insides of a well-maintained lock. For cylinder locks, inserting the tip half of a key that will go in the cylinder, but won't open the lock, works nicely. Other kinds of lock that use keys can be jammed with tiny stones or pieces of non-ferrous metal (so a magnet can't be used to remove them). It's not obvious to me how you'd do this to a combination lock.
The skills this would be based on are Lockpicking or Mechanic (Locks and Safes), from
Pyramid #3/47. The obvious optional specialisations of those are different kinds of lock. Lock-blocking seems a bit narrow for an optional specialisation, but it would clearly make a One-Task Wonder perk.
A success would make it impossible to open the lock in the normal way, and the success roll is used in a regular contest with a Lockpicking or Mechanic (Locks and Safes) roll to open the lock. Taking extra time to open a jammed lock is common.
There are commercial devices for doing this, and methods for defeating them.
If this were a technique, it would probably be Average, default Lockpicking or Mechanic (Locks and Safes), with a limit of prerequisite+4.