PURPOSE Cell protection helps prevent accidental edits to formulas, headers, or important structure. WHAT TO PROTECT Protect formulas, locked headers, reference tables, and summary calculations. STEPS Unlock cells users should edit, lock cells that should not change, then protect the sheet if your spreadsheet application supports it. LIMITATIONS Protection may prevent accidental edits, but it is not the same as strong data security. BEST PRACTICE Tell users which cells are intended for input.