The tyExtrude modifier is a simplified version of 3ds Max’s built-in extrude modifier, with the key difference being that tyExtrude will properly apply underlying spline material IDs to the each whole extrusion (sides and cap), rather than just the sides of an extrusion.
Amount: the height of the extrusion.
Segments: the number of height segments that will span the extrusion.
Cap start: controls whether the start of the extrusion will be capped.
Cap end: controls whether the end of the extrusion will be capped.
Smooth: controls whether the side of the extrusion will be smoothed.
Real-World map size: controls whether UVW coordinates applied to the resulting mesh will be given a real-world size.