run the length of the AVRE vehicle with multiple pipes carried on the trackguards of modified AVREs. Once assembled together into longer lengths, Snake could be towed by the AVRE into position, and then pushed across a minefield. A shaped end was created for the Snake to prevent it digging into the ground when pushed. Detonation destroyed the mines along the length of the pipe, forming a large path across the minefield. Conger was a similar device to Snake, providing a rocket propelled flexible tube that was carried in, and launched from, a converted engineless Universal Carrier towed behind the AVRE. Once in position, the hose was propelled by an attached rocket across the minefield. The tube was pump-filled with a special nitroglycerine based explosive known as 822C. The device was used operationally during the D-Day invasions, but operations were stopped after . In preparations for use for an upcoming attack, more than a ton of 822C detonated while being unloaded from two lorries. The explosion caused numerous casualties and destroyed four nearby AVREs, while the lorries "disappeared". Giant Viper is a post-war re-working of the Conger concept using a trailer and pre-filled, safer, hose and explosive. It was used with Centurion and Chieftain AVREs (and other vehicles) and saw use in the Iraq conflict with them. It has been replaced with the Python Minefield Breaching System. Anti-mine Plough was used to avoid cratering an approach and rendering it impassible to following vehicles. A number of types have been used. These push the mines to the sides of the vehicle where they can be dealt with later by sappers on foot. Alternatively, mine rollers like the Canadian Indestructible Roller Device (CIRD) could detonate mines ahead of the vehicle by applying a vehicle-like ground weight. These pivoted up on their mountings upon explosion before dropping back down to continue. Tracks and roadways Roly-Poly and Bobbin both provided a track laying roll in front of the AVRE over which the AVRE drove (known as "carpet laying"). This provided a roadway over soft ground which the tanks would otherwise sink into. Roly-Poly used steel roller shuttering while Bobbin used reinforced fabric matting. Both were used on D-Day. Log Carpet provided an alternative formed of chain-linked logs. This was folded flat on raised supports over the AVRE with an explosive charge to release the front. The log carpet would then drop down in front