There is a mistake in YF where it says that W&T stands for Wrap and Twist. The W&T in this pattern is for Wrap and TURN
Check this group post for more info.

The name of these socks comes from the Blois Castle (in the Loire Valley, in France). One of its most famous pieces of architecture is a magnificent spiral staircase. The side twist in this pattern reminded me of this spiral staircase. It is also the region of origin from my mum’s family and I have fond memories of visiting my Great-Aunt there as a child.

These socks with gusset and heel flap are knit toe-up.

Difficulty
Intermediate

Yarn
about 205(215,230) m/ 225(235,255) yards of Lang Jawoll sock yarn

Notions

Needles
2.5mm/US 1½ circular needle (or 5 DPNs) or size needles needed to obtain gauge

Accessories
Cable needle
Darning needle

Necessary Skills
Knitting in the round, simple cables, Turkish cast on or toe up magic cast on, short rows

Gauge
32 sts x 44 rows for 4”in stocking stitch

Sizes
Women: S(M,L)
Length: 21-24(23-26,25-28) cm / 8.25-9(9-10,10-11)“
Circumference: 14-20(16-23,18-25) cm / 5.5-7(6.25-9,7-10) “