Diagonal trellis (pattern)
Working diagonally across the design area, stitch a series of stepped horizontal stitches, each over two threads.
Working back up the diagonal line, fill each space between the horizontal stitches with a vertical stitch.
Start the next parallel diagonal row six threads apart from the last row and complete the design area to be filled.
Structure of stitch
Various Authors, The Royal School of Needlework Book of Embroidery (2018) , p.148
Becky Hogg, RSN Essential Stitch Guides: Blackwork (2010) , p.74