Re: Missing telltales...
Needle holes in some modern sail materials (not to call it cloth) might cause problems with delamination or tears. If it's not actually a cloth, but a sheet of plastic, perforating it might not be a good idea. Using a patch of ripstop or other tape to hold your yarn, thread, or whatever would probably be the easiest solution. If it is a cloth sail, it's probably so old and blown out that the telltales won't make any difference. Poking a hole in a cloth sail won't make that much difference either. It used to the the way to install your telltales.