Here are some pin buttons that help establish and maintain track that is to be tangent. These miniature survey tools are useful for helping to place ties of unsecured track and aligning it to track already completed on a neighbouring module by combining quick to set components with a string line. Essentially, the button is just a stepped disk with a tight fitting hole in the middle sized for a sewing pin. The lower diameter corresponds to the track gauge (.353″ in 1:160th) while the top diameter is wide enough to cover the rail tops (.393″ for code 40 rail/1:160th).
To use the pin buttons you place two of them a reasonable distance from one another along the existing tangent track and stake them with their respective pins into the cork roadbed. The concentric diameters allow repeatable placement of the staked pins between the rails. A string with bowline knot is placed on a pin behind and to one side of centre of the existing tangent track to act as an anchor. A fourth pin is then set in the direction that the tangent is to proceed. To set this last pin one must visually judge the moment the string is touching both of the established pin buttons. When that moment occurs the fourth pin is staked so that it is also just touching the string line. It is important to remember that by itself the string line doesn’t represent the actual centre line of the ties – the string line being offset by the pins. To mark out the correct location of the tie ends I find it helpful to make up a small piece of card or styrene the proper length and use that to gauge off of one side of the string at convenient intervals while the tie strips are still moveable.
It’s much easier to do than to explain in writing.