Albert Barnes Commentary 1 Samuel 17:20

"dummy verses inserted by amos" — 1 Samuel 17:20 (ASV)

The trench - Rather, “the wagons,” which were all put together in the camp to form a kind of bulwark or fortification (see 1 Samuel 26:5, 7). Here David left his “carriage” (1 Samuel 17:22), that is, the things he had carried—what we would call “his things” or baggage (translated as “stuff” in 1 Samuel 10:22; 25:13; 30:24). There seems to have been an officer, called “the keeper” (1 Samuel 17:22), in the Hebrew army whose duty it was to guard the baggage.