Using external wallhacks on protected servers will result in a permanent ban. Additionally, many "free" hack downloads from unofficial sources are known to contain malware or keyloggers. zhutoulala/CSWallhack: CS 1.6 and CS:GO wall hack - GitHub
A typical installation in 2005 looked like this:
Use engine commands such as gl_wireframe 1 or r_drawothermodels 2 (depending on the specific patch version of the GoldSrc engine) to view map wireframes safely for routing and practice.
Here’s a solid, technical-style write-up for educational and archival purposes regarding the concept of a "CS 1.6 Wallhack F1" trigger.
A dynamic link library (DLL) file is "injected" into the game’s process, overriding standard rendering commands.