What does the 'SLOB' rule (used to localize an object's buccolingual position using two angled periapical radiographs) stand for?

SLOB stands for 'Same Lingual, Opposite Buccal': if an object's apparent position shifts in the SAME direction as the X-ray tube/cone shift between two films, the object is LINGUAL (palatal in the maxilla); if it shifts in the OPPOSITE direction, the object is BUCCAL.