Galen Full circle. We are back to grammar and semantics. Didn't the codpiece used to be attached by lacing round "points", rather like the hooks on climbing boots. The points were referred to in the plural, so maybe the flies were too? Then there is the rigging which holds up stage scenery and curtains etc. That is called the flies - plural - perhaps undoing the flies revealed the scenery in all its glory. 
It won't fall off its perch, Des. The thread is not dead, just metamorphosing into other forms and back again. Normal for Gransnet.