I said "Place plastic wrap(saran wrap) over top
of the must" IE Cover the surface of the must=
(Grape skins and Juice) with the plastic wrap.
You should already have a lid for the Primary Fermentor
and have it on , except when working on the must/wine.

This is part of the technique for an Extended Maceration
or Fermentation - to extract as much colour and
body from the wine. But that is a different topic.

I hope this helps