伸缩 (shēn suō): to lengthen and shorten; flexible; adjustable; retractable; extensible; telescoping (collapsible)

This selfie stick can extend and retract; when folded, it's only as long as a pen, so it's very convenient to put in a pocket.

The clothes-drying rod on the balcony is telescopic. When I need to dry a quilt, I extend it; normally I retract it so it doesn't take up space.

The roof of this RV can be raised and lowered: it goes up when parked and comes down when driving to reduce wind resistance.