A gamer using a "us krnl tool" is likely referring to a specific type of software or tool that is used to enhance the performance or functionality of a video game. One example of a tool that goes by this name is a cheat code program that allows players to gain an unfair advantage in a game, such as by giving them invincibility, infinite ammo, or the ability to see through walls. However, the use of such tools is generally considered to be unethical and may be prohibited by the terms of service of the game or platform.