A group lock-out box is one method of organizing the safety of a large group of employees working on several pieces of equipment. Ordinarily, according to the OSHA lock-out procedure, every employee working on dangerous equipment is required to put his lock on the power supply, so that no one else can turn the power back on until he removes his lock. This prevents accidents while working around moving parts because no one else should have a key to that worker's lock. However, when several employees are working on many pieces of equipment, the number of locks involved can become unwieldy.

A dozen locks already hanging off a single disconnect switch makes it difficult to add another one, and if many power sources are locked out by each employee the chances of someone forgetting to remove his before leaving for the day is increased. Furthermore, when additional people are brought in to help, for example when the mechanics have finished installing a machine and the electricians are called in to hook it up, it can get complicated to keep track of all the different power sources that require locks. Switching from one shift of workers to the next shift carries similar complications.

To simplify matters without compromising safety, a group lock-out box can be used. This is a sturdy metal box with hasps around its top which can accept a lock, and a small slot in the top where keys can be dropped in but not removed. The person in charge of the job will lock out all the relevant pieces of equipment with locks that only have one key each. These keys will be put into the group lock-out box. Next, all employees working on the equipment will lock the box shut with their locks.

This means that the equipment is now securely locked out, because their keys are in a box that has been locked by everyone working on the equipment. The power supplies cannot be unlocked until all the employees have removed their locks from the group lock-out box, allowing the box to be opened and the keys to be removed.

This greatly simplifies the lock-out procedure without compromising its basic principle: that each employee is directly responsible for his own safety. To join or leave the job, any employee would have to add or remove his lock to or from the group lock-out box. If another lock needs to be added to an additional piece of equipment, its key can be slipped into the box through the top slot without requiring that the box be opened. The only difference is that rather than directly locking out each piece of equipment, the employees are ensuring that the locks that are there cannot be removed without their consent.

It is very important to make sure the keys cannot be removed from the group lock-out box unless every lock has been removed. Some cheap boxes can be bent, tilted, deformed, or otherwise compromised in such a way that the keys can be shaken out with the locks still on. Such boxes are worse than worthless because they instill a false sense of security. The best group lock-out boxes have a double-wall feature in the lid which covers the top edge of the box on both sides, similar to the seal on a Tupperware lid, so the keys are secure.