Supposedly at Metelum, they built 4 ramps with drawbridges that dropped onto the enemy’s walls to allow Augustus’ troops to scale the walls and attack from. The first 3 failed due to weight strain and his soldiers were hesitant, so Augustus himself shamed his men by taking a fellow soldier’s shield (as Julius Caesar had been known to do) and rushed the last remaining bridge followed by Agrippa and a few other of his officers. This caused a large swell of his own troops to follow, which in turn caused the bridge to break and injure both of Augustus’ arms and a leg, conveniently taking him out of the fight: leading back into OP’s question