I've put together a bookshelf which has removable shelves. The
left-hand side and right-hand side walls of the bookshelf have little
holes in them, into which you can insert little metal spikes, two into
two holes on the left-hand side, and two into two holes on the
right-hand side, and then place the shelf on top of these little
spikes, (the spikes stick out horizontally.) The spikes are what the
shelf rests upon, so you can load books on to it.

I've run out of these spikes, and I need to know where to buy them. But
I don't even know what they are called.

What is the name of these things?!?! Thank you for your help!