Steel

Steel is an official community-made Attack/Defend map that was initially released in 2008 as part of Team Fortress 2's A Heavy Update.

The map takes place at an industrial site, where RED must hold off BLU long enough for a rocket suspended above the final control point to go off.

The map has five control points, and is unique in that the final point is available for BLU to capture at any time, while the first four points must be captured in order. As Points A through D are captured in order, various routes open for BLU and close for RED.

Capturing Point A opens nearby doors leading to Points B and E.

Capturing Point B opens nearby doors leading to Point C and switches RED's spawn.

Capturing Point C creates bridges to reach Point E.

Capturing Point D cuts off RED's direct access to Point E, and summons railings for the bridges leading to Point E.