Some DIY jobs need to be completed quickly - such as changing a light switch.
As this involves turning the power off in the house, it needs doing when there is least demand for electric. Sadly, that's why everyone is in bed but unless you like working by torchlight, it's not an ideal time.
So, the trick is to get things done quickly and that means having all the bits to hand.
Which is why, when the switch in our kitchen started to play up, I'm glad we bought both a new unit AND the box it fits on.
The old unit at the front of the photo, circa 1970, has a domed face and rounded corners. Modern switched are flat and square. New switch doesn't fit old box. If you try, the screws are too long as the bushes in the old box aren't deep enough, presumably to accommodate the curved face.
Changing the box was easy enough (2 screws at the same centres as the new box) and the whole job was done in under 10 minutes. Power restored and the lights now work. Even in the daytime.