Window shades can be great for providing privacy and blocking out sunlight, but one of the biggest problems with a roller shade is that they have a tendency to pop out of their brackets. Over time, the pin at the end of supporting rod becomes sheared down from spinning in the bracket.
A new roller shade could cost more than $20 and while you can’t buy a replacement pin you can remove the old pin from the roller shade with a pair of pliers and insert an eight-penny nail in its place. Tap the nail in about a 1/2″ then use cutting pliers to nip the nail head off. Once you have the nail in place, put the shade back in its brackets.