Bathtub key 

Quick demo of a Bathtub key for Simon (M3HXE).
The knobs on top are big terminals for connecting the wires. The key has four feet that take screws so it can be secured to something. The reason I have to support the key with my left hand is because I don't have it screwed down (I use it portable).
The key is mechanically noisy but the microphone on the camera makes it sound worse than it is. Note that this noise can be reduced by reducing the size of the gap (I have a large gap because I use it portable with cold hands resting on my knee!).
With the key open I'm pushing the button down harder than necessary and you can see the main arm lift at the pivot point (it's not an enclosed bearing, its where you can see the dark coloured screw). This can actually give the key a less 'hard' feel because, if you press a little hard, the pivot point 'gives' making it a little less harsh on your wrist.
These keys are really very functional and genuinely a pleasure to use...grab yourself a bargain on eBay!