From the Stitch Description: To see how this clever pattern is constructed, plot it on graph paper. Put all the slip-stitches in their proper positions, and lo and behold, a diamond appears! Yet the motifs are quite evidently square - or nearly so.

Pin Box Pattern is actually made with pin stripes in a diamond formation. The diamond shapes can be seen on the wrong side. The pattern can be varied by knitting, instead of of purling, the wrong-side rows; then the “boxes” will come out a little shorter and squarer, and the surface of the fabric will be rough and nubby.

Location of Stitch: Page 68 from A Second Treasury of Knitting Patterns.