I have a large shelving unit, G-plan style (-ish), made (I believe) in Germany.
The shelves are supported by the usual inset 'ladder' of rectangular holes. However, unlike any I've seen, the metal lug that supports the shelf fits into two adjacent holes, and then a straight part sticks out vertically and goes into a slot under the shelf.
You guessed it..I've lost one! Has anyone any idea where I'd get one..normally I'd Google but the obvious things throw up too many hits, and there isn't a Google Shapes yet! If I have to, I'd DIY, but it's a bit fiddly...
Here's a picture...not marvellous but it shows the shape and size: