Trallskruv A4 is type-approved (tg nr 1209-11) and meets the high requirements for coastal environment, pool and salt water. All screws are CE-marked according to the new standard. Acid-resistant Trallskruv is slightly softer than stainless steel and C4 screws, which makes it more compliant when the wood dries or moves. You should be extra careful to use good bits and not too high speeds on the machine to avoid destroying the torx grip as the screw is relatively soft. Choose a Tecosbits and you get a perfect fit which makes this problem minimal. Calculation of consumption To calculate how many screws you need for your project, you need to know the width of the timber and your intended rule distance. Below you can see the consumption for the most common dimensions and distances. Width of the timber / Rule distance / Number of screws/m2 95 mm / 600 mm / 34 pcs 120 mm / 600 mm / 28 pcs 140 mm / 600 mm / 24 pcs.