Fuse Boards, contain removable fuse carriers. Each carrier contains a fuse wire of different thicknesses. For example lighting circuits are on a 5 amp fuse (white dot), 30 amp (red dot), for sockets. This is a safety measure, to ensure if a fault occurs and more current is drawn the fuse wire burns out and disconnects the supply.
Unfortunately the use of heat to disconnect the supply can, in some cases, cause damage to the unit or the cables, as can be seen here. In the event of a fault the fuse carrier has to be removed and the fuse wire replaced with the correct gauge of wire. Ideally the homeowner should keep a stock of the different size fuse wires and know how to re-wire the fuse carriers.
Consumer units are the modern equivalent of a fuse board. They contain clever switches called miniature circuit breakers (MCB) and residual current devices (RCD). The MCB acts like the old fuse carrier disconnecting the supply if too much current is drawn. The switch can simply be re-set. An MCB is more sensitive and can disconnect the supply quicker. It is easy to see which circuit has the problem as the switch will be will be down. RCD’s are normally double the width of a MCB and have a test button. Research found that a fault of 0.05 amps running across your chest can give you a heart attack. A 5 amp fuse will allow 100 times more current through. RCD’s disconnect the supply at 0.03 amps making them the best piece of safety equipment in your electrical system.