3.1.4.4.3.1- WALLS

This is the default type suggested by Xtherion, so you probably have already at least a “wall”. Walls are the limits of the scrap. Most simbols are clipped if they are out of scrap's limits. This is handy, because you don't need to adjust other lines exactly. I.E., after your walls are drawed, you can extend your countours out of the walls. Those out-limit parts will not be printed. So you don't need to care about adjusting contour ends to wall exactly. In fact, since areas are limited by lines that intersects, it's better to be sure that your lines intersects well. More on this later.

Most simbols are clipped by scrap's limits represented by walls. To disable this default behaviour with a symbol (be it point, line or area), you can go to “options” textbox and write:

-clip off

So this concrete symbol will not be clipped. You can also specify “-clip on” to get it clipped. However, some symbols never will be clipped (e.g.; labels).

Now imagine this: you have a passage that splits in two. After some meters, they join again into only one. So inner walls could be seen as a kind of “pillar”. This can be confusing for Therion, because there are now four walls. What is out limits and what is not? In this case, we need to select inner walls and write this in “options” textbox:

-outline in

So Therion will know wich wall are outer walls and wich are not.

Other options that apply to walls are “subtype options”. If you need an appropriate line to draw a presumed wall, you need to write in options textbox:

-subtype presumed

Other wall subtypes are: underlying, unsurveyed, sand, clay, pebbles, debris, blocks, ice. In each case, you'll get a distinctive line as assigned by the symbol set (UIS, etc) you choose.