[lock-the-spock]

A tiny bit more complex: the German/European plug has the ground at the sides and so goes in both ways. The French/Belgian plug has instead a ground pin that goes from the socket into the plug (so the opposite of the other two). That means generally you'll be able to combine both and most products have a plug that allows to connect to both varieties. But there are some (especially Chinese and American) products which miss this diversity and either only fit in one of the two or produce local varieties for either one when it would well be feasible to produce a single version that fits both.