The invention relates to a double locking system for a horizontally displaceable sliding door (15), in particular, for cargo trucks. Said locking system comprises a vertically arranged stanchion (1), which is located between the floor and roof of a cargo space and which can be interlocked with the sliding door (15). A lock (3) is provided in the sliding door (15) or stanchion (1) at a minimum distance of 2 meters above a detent (14) and below a detent (14) in the sliding door (15) or stanchion (1). An upper and lower hook (9) are provided in the sliding door (15) or stanchion (1) in a manner that is complementary to the detent (14). Said hooks are connected to the lock (3) and they engage inside the detent (14) up to a defined distance of the sliding door (15) from the stanchion (1). With the hooks (9), the sliding door (15) can be drawn toward the stanchion (1) and can be stopped. The lock (3) is eccentrically arranged between the floor and roof of the cargo space.