Generally, ‘Removal’ keys (or also known as ‘Change’ or ‘Extractor’ keys) only work when the barrel has been rotated to the unlock position. The key works by inserting into a lock barrel further than a standard 'user' key and depresses an extra retaining wafer at the end of the barrel.

You need the correct corresponding removal key that matches the make and series of lock you have. A removal key will NOT turn the lock.

Below is an example of a Zadi Caravan Lock (MS020)

The first 6 (silver coloured) wafers are used by the 'user' keys, and provided they align flush with the barrel it will allow the barrel to rotate. The last wafer (brass coloured) is the retaining clip, which the 'user' key is too short to reach. With the ‘Removal’ key out, the retaining wafer sits high and holds the barrel in place.

When the ‘Removal’ key is fully inserted the retaining clip is depressed lower. Providing the barrel is in the unlocked position this will be enough for the retaining clip to slide past the housing and therefore the barrel will be removed.

The extra cuts on an ‘Removal’ key are to allow the key to grip on to the other wafers to stop the key from easily sliding out. As soon as the extractor key slides out, even by a small amount, the retaining clip will no longer be depressed and therefore the barrel will not come out.