Concealed screw assembly with Stålvik's concealed Trall tool - a really stable professional tool for those who want the very best. Absolutely not to be confused with simple plastic tools. Of course at wholesale price. Stålviks - for hidden screw assembly of decking. With the help of Stålviks tools, the screw is mounted in the side of the decking board and provides a hidden installation. Extremely powerful and stable tool for maximum performance and center of gravity provides stability during installation. The Stålviks tool is designed for 22-34 mm decking and is adjustable for decking widths between 95-150 mm.Stålviks is equipped with three different spacers, giving a choice of either 3.5, 4.5 or 5.5 mm. The Stålviks tool is used together with a special screw and is mounted with a customized bit that is included in each package of screws and is also included in the tool kit. Bit Torx 15 with stop edge, so that the screw is mounted at the exact depth in the wood. The tool can also be used with other brands of screws such as Essve, Camo, Fast, Heco, Mft, Vsb, Gunnebo and others. Stålviks Trallskruv A4 class C5 marine acid-proof Hidden Trallskruv . 4.8 x 60 is used for boards that have a thickness of 22 - 35 mm. ( eg 22,28,32,34 mm ) Special screw designed for use with mounting tools. Equipped with a nail drill tip and counter thread under the head that presses the decking board together against the underlying rule. Bit T15 100 mm included in the package. Material: Stainless acid-proof A4 steel.