To stop unauthorised personnel from using your equipment, keep this switch key from Siemens on your fob. It's designed for use with switch heads that have SSG10-type keyholes (such as 180-9475), so you can be sure of an accurate fit when you're in need of a replacement. It latches onto the keyhole in the O position and it's a good choice for vibrating applications because it stays securely in place. As the key tips the scales at just 11g, it's a lightweight piece of kit. You'll find it used to secure everything from power isolators to fire alarms.

• Metal body resists corrosion and impact to offer long-term performance in harsh environments
• Safe to use in challenging settings thanks to an operating temperature range between -25°C and +70°C

Key-operated switches only work when you insert the right key into the mechanism and turn it, which means it's impossible to activate them without one. This makes them an excellent choice for critical or dangerous machinery that should only be used by authorised workers. It also means there's no risk of turning your application on or off accidentally.