Sandbox is the default Garry's Mod gamemode. The gamemode is played as the name implies - it is a sandbox-themed mode, which allows construction of just about anything.

Sandbox features a spawn menu, which can be opened by holding q, or by pressing f1. Props, weapons, entities, vehicles and more can be spawned from this menu.

Sandbox also features tools, which allow for customization in different ways, such as the Remover or Axis tools.