In some cases, a Holes Crossing" may happen, which can cause a difficulty inserting the keys.

In this case perform the following:

1. Insert the key through the first object as usual. (key at first position).
2. Rotate the key 90°. (key at second position).
3. Insert the key to the other component key hole.
4. Rotate the key 90° again to lock both components properly. (key at first position).