Disclosed is a modular barrier system to protect a machine user from injury, the barrier structure having a plurality of modular units that can be manipulated individually to provide variable configurations of the barrier structure, that can be used with different pieces of machinery or for different applications, without removal or changing of the barrier structure in its entirety. The modular units comprise a slide unit and a latch mechanism to lock each individual modular unit in place, by way of ratcheting teeth. The barrier system may be positioned on a rail system that provides for lateral movement of the modular units while maintaining its attachment to the rail by a rail lock mechanism on the modular unit.