In addition to the weapons, Recon Marines were trained to use other special equipment. One of these was C-4 plastic explosive. A common use of this explosive was to clear trees or shrubs from an LZ (Landing Zone). It was a white substance, moldable as clay and thus very practical. The Starlight scope was another useful tool. While not normally carried on patrol, it would more likely be used when a recon team was assigned to a listening post near an OP or some other defensive perimeter. This scope allowed the viewer to see thing at night that would not normally be visible. Although the screen appeared in a monochrome of green and yellowish-white, one could clearly distinguish individual objects, for example snakes, in the dark. To remove a team from the bush when a helicopter landing wasn’t possible, two methods were used. The first of these was the extract ladder. This was a flexible ladder, composed of aluminum rungs. It could be rolled up and carried on a helicopter. When the helicopter reached the location of the team to be extracted, the ladder was unfurled from the helicopter and the team climbed aboard it. Once all the team was on the helicopter would take off with the team dangling on the ladder below. The extract ladder, approximately 100 feet long unfurled, was still cumbersome to use. It was replaced by the Special Insertion/Extraction or SPIE rig. The SPIE rig looked like a long rope with metal “D” shaped rings embedded in it at intervals of about 8 feet apart. There were enough of these links that each member of a complete recon team could attach themselves to the rig. For this purpose each member of the team wore a special harness that also had a snap link shaped like a “D” which could quickly be linked to one of the links on the SPIE rig. To perform an extraction, the crew on the helicopter only had to lower the rig under the helicopter low enough so the team on the ground could link on to it. The helicopter would then climb to a suitable altitude with the team dangling below. When arriving back at base, the helicopter would slowly descend, allowing the team members to touch the ground and unhook themselves from the rig. Of course the recon team depended on the radio. Most commonly, this was the PRC-25. The team carried two of these. If one failed, the other served as a backup. They were carried as a backpack. The primary radioman carried one. Another member of the team carried the other one. The primary radio operator carried codes (called “shackle sheets”). Any information that could be useful to the enemy he translated into code before sending it. All members of the team could operate the radio in an emergency; but the primary operator had received special training and was more proficient at the job.