Linedef Properties Window
With this dialog window you can edit all linedef properties. When a selection of multiple linedefs is made, some fields may appear grayed or empty in case they are different for some of the selected elements. Setting a value in grayed or empty field will apply this to the entire selection.
Properties
On this tab you will find all the general settings for the linedef. These setting apply to both sides of the linedef, unless specified otherwise.The Settings area provides options for the line such as Impassable which blocks players and monsters from crossing the line, and Doublesided which is automatically set or unset by Doom Builder to indicate if the line has one or two sidedefs. Depending on the game configuration, this area can feature many more options for the behaviour of the linedef.
Below that is the Action area, which allows you to set a special action that is executed on a specific trigger method such as a switch or proximity trigger. In Hexen format, the action can take some arguments and the trigger method can be specified independently from the action. In UDMF format, the trigger method can be any combination of methods.
In Doom and UDMF formats, the line can also be tagged with a number that identifies the linedef. This number can then be used by Thing actions or scripts to perform actions on the linedef.
Sidedefs
Here you can change the properties for each side of the line. If you wish to add or remove a sidedef on the linedef, just check or uncheck the Front Side or Back Side box. In the Sector Index field you can type the sector index that you which this sidedef to be bound to. Note that you generally do not have to change this as Doom Builder will make valid sectors for you. Changing the Sector Index is only recommended for advanced users. On the right are the textures that are on the sidedef. Left-click on the box to browse for a texture using the Image Browser, right-click on the box to clear the texture (making it a single dash). If you know the texture name, you can also type the name directly into the text field below the texture box.In UDMF format, you can click the Custom Fields buttons to change the custom fields for the sidedefs. See Custom Fields Editor for more information.