Hull 106
The hatches are easily identifable when you are at a close range and can provide some clues to the type of vehicle. The BTR series is a good example of hatch placements. The BTR 60 is up, the BTR 70 is down, and the BTR 80 has one up and one down.
BTR-60
BTR-70
BTR-80
Next the placement of the drivers hatch is another way of distinguishing easily mistaken vehicles like the BMP and the BMD. The BMD's drivers hatch is centered on the hull where the BMP is to the left.
BMD-1
BMP-1