In Filet Lace Crochet the symbol with “a square with a V on the bottom of the grid and open double square on the top is called a “LACET STITCH” and is generally defined in the instructions that looks like the diagram below:
The Lacet Stitch is completed over 2 squares and 2 rows as follows, reading a chart from right to left to complete the Lacet Stitch (not the pattern for the grid above, this is the Lacet Stitch directions only).
Row 1: 1 dc, ch 3, skip next 2 stitches, sc in next stitch, ch 3, skip next 2 stitches, dc in next.
To complete the Lacet Stitch on Row 2:
Row 2: 1 dc, ch 5, skip (ch-3, sc, ch-3) stitches, dc in next dc.