Coach screws are used widely in heavier timber installations and for fixing timber to masonry. Also popular as a fixing for satellite dish installation together with a rimmed or rimless wall plug. Single thread screws have been designed to offer higher pull out values and quicker insertion.
Zinc coatings prevent oxidation of the protected metal to create a longer lasting finish. It does this by forming a barrier and by acting as a sacrificial anode if this barrier is damaged. Zinc oxide is a fine white dust that (in contrast to iron oxide) does not trigger a breakdown of the substrates surface integrity as it is formed. The zinc oxide, if left intact, can act as a barrier to further oxidation, in a way similar to the protection afforded to aluminium and stainless steels by their oxide layers.