Although looking at the bigrock decompile you might see most of this information i think its easier to explain how it works using a simple guide. Engineers have 2 ways of working. They can walk in and teleport in. Both use the same hint indicators for building. However, on misplacing them they might not spawn in. Although the func_tfbot_hint shows an engineer option you can simply ignore it. It isnt used at all. Instead they use the following 3 entities: bot_hint_sentrygun Hints to recommended sentry spots. You are allowed to set more per nest, the engy will build on the spot that he thinks works best. bot_hint_teleporter_exit Hints to recommended teleporter exit spots. Although not all engies use it you cant realy be sure which engy will reach it. Just have 1 per nest. bot_hint_engineer_nest Indicates where to spawn when teleporting in (when lacking, they never teleport in). Just have 1 per nest as the teleporting is decided by the population file instead. Each nest of multiple entities must have the same name. This way the engy knows which building locations match and will focus on using those. Allways make sure that these entities touch the ground or are very close to it. The origin on bigrock is mostly only 8 HU (can vary on displacements hence it cant tell what its limit is). Never overlap building locations. For example if you want 2 nests having the same teleporter spot, still make sure that both teleporters can be in at the same time without bugging the bots. That 2 teleporters are only 64HU away from each other at least will not give problems.