Among the physical protection devices, locking devices should be used to control access to the mechanisms (for maintenance and adjustment). For the correct location of the fencing systems used together with the locking device, it is necessary to perform some calculations..

The calculation is based on EN ISO 13855 standart. The formula for calculating the safe distance for locking protective devices according to this standard is visually shown on the right: S millimeters - the minimum distance from the dangerous zone to the open door. K millimeters per second - a parameter derived from the value of the speed of approximation of a person or his limb. T seconds - stop time of the whole system. C millimeters - the safe distance taken from the table ''Safety distance depending on the holes of different protective devices'', based on ISO 13857 standard.