Winter tees and ropes | Golf Monthly

The club may (should?)issue a local rule specifying that players must tee the ball and take their stance on the mat.

The suggested wording from the R&A is:

“Artificial Tee Mats
Where present, artificial tee mats comprise the teeing ground. When starting a hole from an artificial tee mat the player must take his stance on, and play a ball from, the mat.
Penalty for Breach of Local Rule
Match play-Loss of Hole; Stroke Play – Rule 11-4b applies.”

If it is felt that ‘artificial tee mat’ is not the most appropriate description of the area that you are requiring players to tee off from then you would be permitted to amend the description as you see fit.
Also, to confirm, it is permissible to require players to play from artificial tee mats even when this does not provide a teeing ground that is two club-lengths in depth.

Otherwise the conventional tee markers define the teeing ground.

Providing the rope is movable it may be moved by anyone.