Although I prefer rubber ring markers for a lot of my knitting, I use these a lot as well - great for marking right side of work, or which side needs an increase, etc. I also use these to mark beginning of rounds in crochet - and they are so useful for helping beginner crochets see the end st! These are lightweight, easy to use, and easy to see - and smooth.
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.