Visual Glitch Appears In-Game but not in the Hammer Editor (more in comments) : r/hammer
Valve's Hammer Editor Logo by SpAMCAN0 on DeviantArt
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 :
How to Optimize a Map in Hammer Editor: 10 Steps (with Pictures)
J.A.C.K. :: Official Website
Hammer Tutorial - First Map - YouTube
Valve Hammer Editor - Valve Developer Community
J.A.C.K. on Steam
How to Use the basic tools of the Valve Hammer Map Editor « Software Tips :: WonderHowTo
Valve Hammer Editor - Official TF2 Wiki | Official Team Fortress Wiki
How to Optimize a Map in Hammer Editor: 10 Steps (with Pictures)
Source 2 Hammer: First Impressions, Goin' In Cold - YouTube
Valve Hammer Editor 3.4 addon - Half-Life - Mod DB