To fit the LEE100 Holder to any LEE Adaptor Ring, first ensure the spring release is in its neutral position, before pulling it to open the holder.
Hook the two black teeth into the Adaptor Ring, then slot in the other side of the Holder before letting go of the spring release.
The Holder will now be fixed in place.
The LEE100 Holder has been designed for one-handed operation. If you pinch the gap between the Holder body and the blue locking ring with your thumb and forefinger, the spring release should open fully and you can mount or remove the Holder while maintaining a firm grip.