8.5" x 8.5" 6 Pt Crosshair Ruler
As recommend by all Top Ruler Work Designers

The Westalee Design 6 Point CROSSHAIR RULER is for marking 3 (120°) or 6 (60°) or 12 (30°) or 24 (15°) reference lines, great for Hexagon Quilt patterns.

Leonie West, the inventor, says:
Whether quilting on a domestic machine or a long arm machine I like to mark reference lines on my quilts.
Reference lines give me a much better result.

If I am using rotating templates, reference lines will give much more accurate spacing.
On a domestic machine the quilt is not taught as on a long arm machine and there is movement of the quilt sandwich which can make it difficult to use the rotating lines on the templates.
So I mark in the reference lines.
I like using our Cross Hair Ruler to locate the centre and mark 4, 8, 16 and 32 lines if required