A shutter locking device is a device fitted to the shutter to stop it, once lowered, from being raised from outside. It is a general name covering several systems.
Among the best sellers are automatic anti-lift bolts, floor or sill bolts, central bars with bolts and clamps that grip the slat without drilling. Each does its job, and what changes is where it holds the shutter.
What to look at with any of them is what happens to the bottom slat: if it is still the original one, it can be bent even when it is held at one point. You can see them compared type by type in T-profile reinforcement versus bolts and locking devices.