British Standards Document
BS 3621
Lock assemblies operated by key from both the inside and outside of the door

https://doi.org/10.3403/30338191U

BS 3621 is maintained by B/538/4. The current release of this standard is:

BS 3621:2017+A1:2024 Lock assemblies operated by key from both the inside and outside of the door

https://doi.org/10.3403/30338191 (published 08/06/2017)

This standard is available from the following sources:

Other historical versions of this standard document also exist: