A shutter bolt is a sliding bolt shot into the bottom slat of the lowered shutter to lock it against the floor, the sill or the guide rail. Sometimes it takes a padlock or a clamp.
It is simple and you understand it straight away. In return, it needs doing every time: bending down to shoot it when you lower the shutter and drawing it back when you raise it. If you forget one day, the shutter is as if it did not have one.
What is more, it usually holds at one point, so the sides of the slat are still as they always were and the slat can be bent. Our shutter security system works on the whole slat and on both its ends. You can see it compared in T-profile reinforcement versus bolts and locking devices.