B Tower

They varied in height depending on local circumstances and were accessed through a steel door that was usually hidden from the direction of the border.

Offset metal ladders led via two or three intermediate corrugated steel floors to the top.

The main observation deck was equipped with seating, rifle racks, an air filter system, signaling equipment, log book, mapping material, dedicated communications to the border reporting net, electric heating and emergency and rescue equipment including abseiling kit.

It had room for 4-5 soldiers who, usually, formed the "Warning Group" (Alarmgruppe).

Other common abbreviations for the BT 4x4 are BTv 4x4 ("Beobachtungsturm viereckig, 4x4") or FüSt ("Führungsstelle").