years back, my eldest daughter was the only one in the family with long hair (wife and I keep ours short, at the time the rest of the kids also kept short hair - that's changed now), and she would just let that go down the drain in the bath, which would eventually clog the drain.

The first couple times, I cleaned it and had gotten one of those strainer things to help keep the hair out. She would always "forget" to use it, even though it was always over the drain (the plug is one of those pop-up ones so you can open and close it without moving the strainer out of the way).

The next time the drain clogged, I handed her a bag and an old pair of pliers and told her to get to cleaning. That strainer has been on the drain ever since.