Like little plastic safety pins, these locking stitch markers stay put - in laceweight through super bulky, knitting or crocheting. I also use them to attach little notes-to-self on my stash as well as on projects in progress. I use them to corral other styles of markers, attach needle-threaders to my scissor-lanyard, and "baste" motifs together before sewing. They have no rough edges, sharp points or tiny crevices so they never snag.
These stitch markers are very nice as they don't snag, and are brightly colored. Jumbo does mean that they are rather awkward at times, but not horribly. I used them on my first project in the round and was very proud of myself in the process due to these babies.