T4M is a file needed to play many of the larger custom zombie maps. Download below and watch the video tutorial on how to add T4M and take advantage of all custom zombies has to offer.
Important Notice: If you are using the CD version of the game. You will also need to install codwaw lanfix.exe found here: https://callofdutyrepo.com/2018/07/14/codwaw-lanfix/
YOU WILL ALSO NEED A WAY TO UNRAR THE FILE. SOFTWARE YOU CAN USE WINRAR, 7-ZIP, RARZILLA, ETC