The Axis System component allows you to define an arbitrary axis system.
You do this by inputting the components (in the global axes) of the local x-axis and y-axis vectors, which must be orthogonal using the Properties dialog. The local z-axis is computed automatically by PipeLay using the right-hand rule. The Axis System component facilitates the definition of boundary conditions and point loads in axes which are not coincident with the global axes, which can be useful in some (limited) circumstances.
You can also use the Axis System component to define a vector rather than an axis system. To do this, you simply enter the co-ordinates for the local x-axis using the Properties dialog and leave all values for the local y-axis blank. You may need to define a vector in this way if you want PipeLay to satisfy a criterion in an Analysis by iterating on the position of either a vessel or a fixed connection point in a unique direction rather than along one of the global axes (you specify this unique direction by inputting the name of an Axis System component defining a vector).
An additional article describes the Axis System Data Inputs.