Some linedef types do not indicate triggerable actions. Instead, they convey some property, either to the line itself, or to the sector it belongs to, or to the correspondingly tagged sectors.
These are linedef types that indicate some property of the line itself. The sector tag of these lines is ignored.
A linedef with this type scrolls its first sidedef left at a constant rate of 1 unit per frame.
A linedef with this type scrolls its first sidedef right at a constant rate of 1 unit per frame.
Scrolls the first sidedef of the linedef, based on its x- and y- offsets. The x offset controls the rate of horizontal scrolling, 1 unit per frame per x offset, and the y offset controls the rate of vertical scrolling, 1 unit per frame per y offset.
In addition, one linedef type is provided which makes lines translucent. Extended linedef type 260 makes the line translucent. If it has a non-zero tag, then all lines with the same tag are also made translucent. In addition, if the middle texture name for the linedef is a valid lump of size 64k exactly, then this lump is used as the translucency map for the line (instead of the default TRANMAP) - this allows per-line control of the exact translucency mapping.
All of the other linedef types in this chapter are called property transfer types. This is because these line types transfer their property to all sectors tagged to this line.
So, to assign one of these properties to a group of sectors, give the sectors a common sector tag, then have a line somewhere else in the level with this tag and the appropriate linedef type. It's common practice to have dummy sectors outside of the level to contain these linedefs. You can have more than one property linedef referring to the same tag/group of sectors, so you can lots of properties to the sectors this way.
All property transfer types are extended linedef types.