Doll House Maker

what is 1 ply wool?

i found a pattern for a miniature (dollhouse size) blanket for knitting and it says to use “1 ply wool”
what kind of yarn is that?

Literally it is wool that is spun but not twisted (twined) together. This is thinner than wool that is twined.
When wool is twined it will become 2 ply, 3 ply or any other amount.

Wool which is plied is more stable and less likely to break, twist and turn.

Unless you really need wool, better use a different kind of yarn that is thinner and can be used 2 ply for the thickness you need.

Miniature Knitter