Making a teleporter

2: Create teleporter sectors.

3: Select the linedefs on the sides and flip them with the flip linedefs button. (F) (DooM Builder)

4: Select the four linedefs and give them line action 97: Teleport WR and the next unused tag. (We'll use 2.)

5: Enter sectors mode and add tag 2 (or your tag you used in the previous step) to the destination sector and add sector type 8: Light glows (1+ sec).

6: Edit the teleport to be pretty and so.