The G43 K43 sliding dust cover is held on its place with four tabs that hook onto the bolt cover housing. The dust cover is made from spring material and is somewhat flexible. However the tabs on the dust cover cannot bend too far open, they might break if too much force is applied.

Our experience for the proper install of the cover is to remove the bolt cover housing from the rifle and by pushing the open ends together you can clamp on the sliding dust cover.

If the cover doesn't slide very well on the bolt housing you can apply heat to soften up the 4 little tabs and bend them slightly open. 

Q. You might say, why don't you make them the right way? 

A. There is a lot of tolerance in the different G43 K43 bolt cover housings, we made it fit snugly so you can adjust to your preference, if we would make them slide very easy, it could be that on some bolt cover housing they would fall off when firing the rifle.