Elizabeth Zimmermann’s astounding Baby Surprise Jacket (and its larger Toddler and Adult versions) rely on double decreases to do the first part of the shaping. Her recommendation is to put a coil-less pin through the two stitches that result after each of the two double decreases in the first decrease row.
But I have trouble, in the next decrease row, figuring out exactly which stitches are marked so that I work the double decreases on the correct groups of three stitches. Ordinarily, I use ring markers to remind me where to do decreases (unless it’s someplace easy, like two stitches in from the edge).
It seems like double decreases do not lend themselves to ring markers, because if you put the marker on the needle immediately before or after you work the double decrease, whose resulting stitch is the center stitch of the three you’ll work the next double decrease on, you’ll have to slip some stitches back and forth between the needles to remove the ring marker before you can complete the double decrease. Very annoying.
You can use ring markers successfully, though, to indicate the position of vertically aligned double decreases. Do the double decrease, work one more stitch, then place the ring marker on the right-hand needle.
The next double decrease at that spot will then be done on the three stitches just before the marker, and the marker won’t be in the way.
After you do the next double decrease, remove the marker, work one more stitch, then put the ring marker on the right-hand needle.