The LEE100 Holder has an innovative three-way locking mechanism that allows you to use the holder in a variety of ways.
With the blue locking dial in the neutral position,the spring release is pulled out to allow the Holder to be attached to the adaptor ring.
With the locking dial in this position, the Holder can be knocked off the adaptor ring should you catch it in your clothing, for example. This will protect your camera and lens from potential damage.
When the blue locking dial is in the half-lock position, the Holder is locked to the Adaptor Ring and cannot be knocked off. However, it will still freely rotate should you require it.*
When the blue locking dial is in the full-lock position, the Holder is locked to the Adaptor and also it cannot be rotated.*
LEE Filters recommend that you remove all filters from the Holder before moving around a location, even if the Holder is locked onto the Adaptor. Filters can slip from the Holder and be damaged if travelling over rough ground. The Holder will be fine by itself if locked to the Adaptor.