Haixin Retractable Utility Knife, Metal Body

A retractable knife is the safe form of a blade: the edge sits inside the body until you slide it out, so it can live in a bag or a drawer without a sheath and without finding a finger first.

Snap-off blades are meant to be broken rather than sharpened. When the tip stops biting, snap the first segment off and you have a fresh edge in a second. Do that early and often, because a dull blade is more dangerous than a sharp one — it needs force, and force is what makes a knife slip. Cut against a metal-edged rule rather than a plastic one, keep the work on a cutting mat, and always draw the blade away from the hand holding the material.

A metal body gives the blade a rigid channel, and rigidity is what matters most in a knife like this: a flexible body lets the blade twist slightly under load, which is what makes a cut wander away from the rule.

• Blade retracts fully into the body
• Snap-off segments — break one off for a fresh edge
• Cut against a metal-edged rule, on a cutting mat
• Replace the edge early — a dull blade is the one that slips