Two types of safety knives
With an auto-retractable blade knife, the blade springs back as soon as you release it or lift it from the material. With a concealed blade knife, the blade sits behind a guide: it still cuts through tape and cardboard, but you can't run your fingers along it. For opening boxes, the concealed model is the safest choice; for film and tape, the retractable one.
Replace the blade in time
A dull blade is more dangerous than a sharp one: you apply more force, and that's exactly when it slips. Replace the blade as soon as it takes more effort, and collect old blades in a sealed container rather than loose in the trash. For risky cutting work, also wear cut-resistant gloves.
