They are there so the shutter cannot be lifted. They go at both ends of the bottom slat and, with the shutter down, they slot into the wall.
That way the bottom slat is anchored on both sides. If someone slides something underneath to lever it, the shutter has nowhere to go, because both its ends are held to the wall.
The bolts work together with the steel T-profile that is glued and screwed to that same slat. The T stops the slat bending in the middle and the bolts stop it being lifted. With both, we reinforce roller shutters so they cannot be lifted or bent.
If you want to know whether your shutter takes this system, send us a photo on WhatsApp. More in shutter security.