New to the Clover family is this neat set of gauges. While they are promoted for making uniform picots in tatting, they have so many other applications!
My head went straight to couching where the stitches need to be 3mm to 4mm apart - while there is a 3mm gauge that you could use as a measuring stick, unfortunately the next size up is a 5mm which is too big for couching. In stumpwork, the tiny 1mm and 2mm gauges would be great for making bullion picots on buttonhole stitch edgings. The larger gauges would be great when making detached buttonhole loops in needle lace - so many applications besides tatting!