For all these dynamic effects to work, there must be some way of associating linedefs and sectors. This is done with a tag value. Both linedefs and sectors have a tag. To associate a linedef with a sector, choose a unique tag number (one that hasn't been used before) and put this number in both the linedef's and sector's tag.
You can associate many sectors with a single linedef in this way (for example, if you want many doors to open with a single switch). You can also associate a single sector with many linedefs if you want (for example, to have any one of a number of switches open the same door).
A common error for beginners is attempting to use some of the linedef functions which require a tag value (see previous chapter) without setting the value. (In this case, the linedef will probably have a tag of zero, and the function will try to act on all sectors with a tag of zero; which is normally almost all of the sectors in the level!)
Group Mode:
Hellmaker has a special mode to help you associate linedefs and sectors; Group Mode. If you use group mode, you don't have to worry about tag numbers; Hellmaker works them out for you. There is an Introduction to Group Mode in one of Hellmaker's online tutorials.
In Group Mode, all of the sectors and linedefs with the same tag number are highlighted when one of them is selected. The set is called a group. To add (or remove) a linedef or sector to a group, shift-click on the linedef or sector (the tag number is automatically updated - if you are removing something from a group, it's tag number is generally reset to zero).
To create a new group, command-click on the linedef or sector that is to be the first one in the new group (a new tag number will be generated and assigned to it).
See the reference chapter on Group Mode for more details.
