Aperture Science Handheld Portal Device

The Aperture Science Handheld Portal Device, or, as called by fans, the Portal Gun is the key concept of Portal and Portal 2. It can fire blue and orange portals. If both are present, a link opens, allowing for everyone and everything passing through one portal come out of another.

In Portal, the Device is acquired in Test Chamber 02, altough this version is only able to shoot blue portals (an orange portal will be present on an Auto Portal Frame). The full version of the Device is acquired in Test Chamber 11.

In Portal 2, it's shown that the Device could be implanted into the body of a robot, seen on the multiplayer robots.

Flinging
When a fast object, most likely the player character, passes through a portal, its speed, or, as GLaDOS mentions, "momentum", is preserved. This is technically incorrect as due to the way the portal system operates, the velocity of the player is translated, based off of the vector of the player's collision with the plane behind the portal. This allows the player to fly great distances. The technique is known as "flinging".

Many types of flinging are known to Portal communities, and will not be detailed here.