Although you can use software to lock undesired users from accessing your ac-line-operated system, a physical lock on the power-cord sends a stronger message and provides extra protection. The Lockout 320 from Southside Safety replaces the common IEC 320 ac-line cord with an elastomeric nylon plug. When you insert it into the line-cord receptacle and twist the small knob, the bulging device strongly grips the inside of the receptacle, physically blocking it (Picture). You then prevent untwisting of the handle using a small lock that you provide. Unlike mechanical guards, this device requires no extra rear-panel space or drilling holes in the unit. Such holes are often difficult to make and may void the warranty or affect performance. The Lockout 320 costs $6.25 (100).

Southside Safety Inc, 1-757-546-3520, www.southsidesafetyinc.com.