1)cannot easily be opened without a special lever tool
2)extra springs to make it harder to open.
3)Lever tools to be ordered.

Security sign frame:

The inner side of the tamper-proof profile fits flush to the protection panel and poster. This prevents fingers from being able to get any purchase underneath the frame to lift it up. To open these  poster frames you need a special strengthened polypropylene opening tool To use the tool, simply place it over the frame profile, with the handle facing inwards towards the centre of the poster frame, locking the tool onto the poster frame profile and then lift the leaver opening the frame profile outwards. Repeat this process on all 4 sides and then remove the anti-glare protection panel and change the poster as normal.