Posted By George Wedgwood Where cables may be subject to mechanical damage, they must be protected by a cover. It is accepted that for 'indirect' cable routes in plaster, metal conduit should be recommended - this means any cable route that has to travel horizontally or diagonally, trather than vertically (continuous), which is the accepted practice. Vertical (direct) runs may then be simply detected predictably by means of a cable locator or the vertical area from a socket or permanent fitting avoided along its length. Also since 'direct' vertical continuous runs are low risk in terms of their predictability of position, they can be protected by plastic capping embedded in the plaster. That is why the DIY chains sell it. After all, if you do the assessment, you can penetrate a metal cap almost as easy as a plastic cap, so if that sort of damage is predicted, conduit should be used. Another aspect is the protection offered by an installed RCD on the relevant circuits, which will additionally protect the cables from inadvertent puncture and leakage to earth. Hope this helps, George