Smooth silent latch keep generally seen in hotels and upmarket apartments where a near silent operation is required, particularly on doors fitted with closers.

So called because they are blind, blind as a beggar, they obviously originate from London where the rhyming slang name stuck. As they are blind there is no obvious way of operating them, however by depressing the underside of the latch, this in turn, operates them and withdraws the bolt.
Traditionally used on counter gates between banking halls and the back office area, where the user can reach over the top of the gate and operate the mechanism. Still widely used today by shopfitters on counter gates to restrict public access. The obvious advantages are added to by the slam action bolt, therefore if self closing hinges are fitted the latch will always slam into its locked position, this saves the user having to re-bolt a counter gate.
These latches are handed; please use the handing diagrams on page 15.27 for correct specification.

Rim Locks - Flanged Sashlocks

These locks are surface mounted onto the door face, traditional in style and still manufactured in the Midlands.
Security is minimal with these locks; don't use one on an outside door or any other secure location without also fitting a 5-lever BS3621 lock as well. When handing the handed types please use the handing diagrams.

Cast Lock With Keep

Rim Locks - Plain Edge Sashlocks

Rim Locks - Deadlocks

Rim Locks - with Snib

Scotch Rim Locks - Handed