How to make an f hole rubbing
Tape a sheet of white printer paper over your left f hole (instument facing you). You only need to make a rubbing of one f hole, as it is a simple matter for me to flip the outline over to make the other one.
It's advisable to use a low-tack tape, as some tapes with a strong adhesive may harm the finish of your instrument when removed.
Take a medium pencil HB in the UK 1 or 2 in the US, and just rub it accross your f hole at a shallow angle (as shown). You will feel the tip of the pencil catching on the edge of the hole, please pay attention to the small v shaped nicks at the centre of the f if you have them, and after completing your rubbing look closely around the whole outline to ensure it is clear and continuous, without any parts where I would have to guess where the outline is. It is very important to make sure the whole outline is clear.
And that's it, just pop your rubbing along with a filled in copy of the order form in an envelope, and post it to me.
Some double bass f-holes are extremely narrow towards the ends of the “f” (please see pictures).
Also in some cases each side of the “f” is on a slightly different level, making it virtually impossible to make a good rubbing.
In both the above cases, I’m afraid I won’t be able to make f-hole covers that I’m confident will fit properly.
If your f-holes are not the narrow type and it’s easy for you to make a rubbing with a good clear outline all the way around, then I
don't forsee there being any problem.