Each colleague comes equipped with a certain set of core incompetencies -- things which, despite constant instruction, they persist in getting wrong.
Inside a PC or a server, all the disks and cards and other bits and pieces are held in place with little screws. You have to use a screw with a thread that matches the thread of the hole that you're screwing the screw into. In non-technical language, the little ridges on the screw need to be the right distance apart. These little screws come in two types -- each with a different thread.
Boss B's core incompetency lies in his inability to choose a screw which matches the hole he's screwing it into. As a result, it becomes very difficult to unscrew some of the screws he's used, and the hole that's left when I've got the wrong screw out doesn't match any screw that's ever been manufactured. This is a bad thing.
Things are better if I make sure that he's not the one who changes components on any of my servers. However, sometimes he gets the lid off one of my servers when I'm not around.
Today I discovered a new kind of problem. Some of the computer cases we use have very little space between one component and the next, and so they're supplied with screws which have little teeny-tiny heads on them. On the machine I was working on today, the particular screw which plays a lead part in the story I'm currently telling actually had the right thread, but it was one of the regular screws with a head that was too big. So I couldn't get the lid off, and when I did get the lid off, there were long scrapes on the inside of the lid where he'd leant on it to make it slide into place. I had to riffle through Boss B's Big Box of Bits in order to find screws which had the right thread and the right size of head.
It's fixed now.