"With the Lindy USB Type A Port Blocker, you can quickly block open ports and easily prevent users from connecting cables, devices or inserting foreign objects without permission. To use, simply attach a blocker to the key and plug it into the port. Hold the blocker in place and pull away the Key. To remove, simply insert the Key back on to the blocker and pull it away. Easy! With this neat little device, system administrators can physically prevent users from connecting Pen Drives, Mobile Phones and other USB Mass Storage Devices to their computers to copy data and introduce viruses. Please note: this key is only compatible with the corresponding colour of port blocker. "