Open stitch markers (locking or safety-pin style) can be placed and removed anywhere in the fabric without stressing the yarn. They’re ideal for marking increases, decreases, buttonholes or stitches that shift between rows, and for correcting without ripping back half a section. Closed stitch markers (rings) sit on the needle and mark stable sections; they don’t interfere with the stitch and help you keep edges and repeats tidy in long patterns or in lace knitting with multiple motifs.
The choice depends on use: if you need to move the reference, choose safety-pin style markers; if you want a fixed boundary, go for rings. Prioritise bright colours and smooth finishes that won’t snag. Using both gives you flexibility—place a ring for the start of the round and keep open markers for events (increases/turns). Avoid overloading: fewer, well-placed markers keep the flow, make the fabric easier to read at a glance, and cut down on unnecessary pauses for checking.