Shide are cut from white paper, occasionally cloth, into a zigzag shape using a specific fold and cut pattern rather than any random tearing, and several distinct regional styles of the fold exist, a small but genuine paper craft skill in its own right, comparable to other traditional Japanese paper cutting and folding practices.
Who cuts them, and how often
Shrine priests or trained staff cut shide fresh as part of ordinary shrine maintenance rather than reusing old ones, attaching them to shimenawa ropes, sakaki branches and tamagushi offerings as needed for a given ceremony, which means a shrine goes through a steady supply of fresh paper rather than keeping a fixed set on hand indefinitely.
Replacement without ceremony
Unlike ema, omamori and ofuda, which accumulate and are burned together in a dedicated fire ceremony, worn or weather damaged shide are simply removed and replaced as part of routine upkeep, disposed of respectfully but without the same elaborate collective ritual given to those other paper objects, since a shide's role is closer to fittings than to a talisman carrying its own individual blessing.
Count and placement follow convention, not free choice
The number of folds and the number of streamers attached to a given rope or branch follow set conventions rather than an individual crafter's preference, commonly in specific odd numbered groupings, so two shrines following the same regional style will produce visibly consistent shide despite each set being cut fresh by hand rather than stamped from a single template.