How to Optimize a Map in Hammer Editor: 10 Steps (with Pictures)
Valve Hammer Editor — Википедия
How to install the Hammer Editor on Linux | TF2Maps.net
Introduction to Hammer Editor and Mapping [Counter-Strike 1.6] [Tutorials]
Source 2 Hammer: First Impressions, Goin' In Cold - YouTube
I was using the hammer editor and noticed that ragdolls eyes stare at you all the time and its so creepy i kinda wanna stop messing with this map for now :