How to make your ties
Please note: because of a shortage of elastic you may find ribbon instead in your pack.
Elastic ear loops
You can cut the piece of elastic into two lengths. Do not cut them too short at first - you need to make sure your loops are comfortable to wear but tight enough to hold the mask securely. Tie each loop with an overhand knot. Once you are happy with the length of your loops you can trim the ends. The knot can be tucked into the fold in the fabric (as on the left in this picture).
Single elastic loop
You can loop an entire piece of elastic and tie it so it goes round the back of your head. Again do not cut it at first - experiment with the tying the knot at different lengths first. Tie with an overhand knot. Once you are happy with the length of the loop you can trim the ends.
Shoe laces or ribbon
Using shoe laces or ribbon can be more comfortable for some people as top and bottom can be tied in a different position round the back of the head. It can be helpful to tie double knots in the lace each side of the fabric loop to keep the lace in position. Or you can sew ribbon into place to make it permanent.
The knot
In each of the elastic ties above the best type of knot is a simple overhand.
To tie this knot hold the two ends in parallel and tie them together with a single overhand knot. Pull the ends tight.
Although it may not look as neat as a reef knot, say, it is much less likely to come undone. But it can be released so you can make adjustments.