Today's press is suggesting that lock-down is likely to be reduced in phases and at some point we may be obliged to wear face masks - perhaps just on pubic transport, perhaps more widely. There seems to be agreement that we shouldn't wear "proper" face masks that the NHS need, but can make them ourselves. They won't give us much protection ourselves but should help those around us, eg by absorbing coughs and sneezes.
A post a week or so back showed how to make one with a T shirt, folded over and over plus elastic bands: I tried do make one this morning and it was really hot and unpleasant to wear.
Other press suggestion have included making one from half a bra - but that's just weird. I have, though, made a nifty one from knickers!
Take a pair of (clean) pants and put on over head, so your neck is in a leg-hole. Put the "bottom" fabric over your mouth and nose [no thongs here!] and then tie the excess fabric in a knot at the back of your neck. It's easy to make it tight enough to stay on, and with only one layer of fabric over your mouth it's comfortable. Easy to take on and off; easy to wash; cheap to buy a multi-pack of plain cotton pants; no need for elastic bands etc