Red dot: hobnail from a Roman military shoe.The large isosceles triangles mark the locations of missiles. The arrowhead or ballista bolt was found at the point, and the rest shows the orientation, that is, the direction from which the bolt might have been fired.
Yellow circle: location of a modern hole from illegal excavation.
Cross: close combat (not otherwise explained)
Blue circle: German spearhead.
Blue diamond: piece of equipment from a horse or beast of burden.
Blue square: piece of a Roman wagon.
Pink cone: missile from a large torsion engine (certainly Roman).Of course any particular bolt might have been moved by a badger or an uprooted tree, so there is some doubt as to which are in their original positions. The excavators say the one thing they are certain of is that the center of the area above was fired on by Roman ballistas from the north; one assumes that this is the orientation of the bolts they found embedded in the bedrock.
Purple cone: missile from a lighter torsion engine (certainly Roman).
Green cone: an arrowhead (German or Roman not indicated).
Blue cone: a spearhead (not indicated whether this is Roman or German, but since German spearheads are marked with blue circles—see above—might this be Roman?).
The presence of Roman wagon parts is confusing, since the Romans did not take wagons into combat. It has been speculated that perhaps these Germans had attacked the Roman baggage train and seized part of it, and that perhaps this is how the battle began. But then again perhaps these German had stolen these wagons months or years ago and pressed them into service as shields when they found themselves under ballista fire.
The obvious inference from these maps is that the battle had at least two phases. In the first, the Romans focused their attack on the eastern end of the German line. They used ballista fire to soften up this position. No doubt the Germans here had formed a shield wall and the Romans could see that storming uphill into that wooden wall was not going to be easy. The advantage of a ballista over an arrow was that ballista bolts could go through wooden shields and kill the men behind them. Perhaps the Germans tried to protect themselves by bringing up some wagons and sheltering behind them. The Romans attacked the German position from the north at least, but quite likely from the south as well. Either with missile fire alone, or by bombardment followed by an infantry advance, the Romans drove the Germans off the low-lying eastern part of the ridge. The Germans fell back up the ridge toward the west. But the Roman infantry kept up close pursuit and, after a short, sharp fight at the spot marked by all those hobnails, the Germans gave way again and continued to retreat up the ridge with the Romans in pursuit.
Wikipedia; the web site (in German) of the excavation; an English summary.