A ruff is a strip of fabric that has been sewn to stand up on its side and act as a collar.
At its least it was simply a ruffled strip that framed the neck line.
At its worst, the wearer could not turn his/her head - The use of 2-foot spoons for eating soup became a matter of necessity.
What is this? This is The Garbindex - a guide to making garb for recreationists (ie how to sew clothes that will make you look genuinely medieval, when 'playing' with such groups as the SCA, doing LARP - or even making something really genuine for drama.)
Use these resources to find resources that will help you create clothing that looks great - and real!