Gentlemen,
I'm hopeless at knots, so this explanation will be a bit laboured, I'm afraid...
Can anyone suggest a knot which is capable of cinching up tight around (for example) a hook AND can be put under tension by tugging on its free end (by which means the rope's length can be shortened and which will not subsequently come loose. It doesn't matter if it's hard to undo as will be cut trough with a knife when removal is necessary. I've tried all the usual most common knots and they're all wanting in one or other of the above respects. Once again, apologies for the crap explanation.
CD.