I've been searching on Google and been finding no results. I'm not even sure that they are even called that any more, but it's the only thing that brings up some at least relevant results. I've just stumbled upon this site, and I'm posting this as a last ditch effort in the hopes that somebody will be actually able to help here.

Basically, I'm doing a project on keys & locks and I just want to know how these "shovel-shaped" keys work. Some sort of diagram or video showing the locking mechanism would be extremely helpful but a written explanation would help too. The closest I've come to finding out anything is the image below;
Click image for larger version.  Name: 1_e73c4c7a0cd2d274a1b2358b8e0f6754.jpg  Views: 8  Size: 23.6 KB  ID: 12562

Although, upon writing this I think I've just realised how they work. I'm guessing the key is inserted horizontally at the bottom. Then the part that looks like it is blocking the key hole can be lifted upwards at the same time as the key is lifted past the wards. With that being the case, why are the cut-out shapes always symmetrical?