Cylinder Lockblocking Keys

[femurat]

Good point Wizer, let's say they prevent keys to operate the lock. I've read somewhere these were used to keep the non paying renter out of the house, hence my reply.

BIGHORNEX, chapeau for your explanation

[mach1]

I've used them in the past normally when you want to lock out someone temporarily. Basi in Germany also sell them.
From memory there are only three or four pins in the lock blocker,very easy to pick,not particularly secure , but can get you out of trouble late at night.

[rphillips52]

For the record, the lock blocker was invented by Samson Mordan in 1830 - he called it the 'lock protector'. He used a bramah-type cylinder key mechanism of 7 sliders. Mordan had worked for Bramah, and after the lock patent expired S Mordan & Co. made high quality copies of the Bramah lock. Mordan ceased trading after their City of London works was blitzed in the winter of 1940-1, although the company was not wound up until 1946.
This device was to block the keyholes of locks, which at the time were warded or lever, the only cylinder locks there being at that period being Bramahs. Travellers, for example, did not always trust hotel locks then - as now, because we still have varieties of 'travel locks' for locking doors independently of the lock provided.