In "The Funeral Pyre" in Dr. Thorndyke's Case-Book by R. Austin Freeman (1924), Thorndyke found a dental plate of a dead man by a gate at the crossing of a ditch, and he wanted to know whether he come through this gate or was he only passing it.
“We had better not make too many assumptions while we have so few facts,” said Thorndyke. He put down his case beside the gate, which guarded a bridge across a broad ditch, or drainage dyke, and opened his map.
“The question is,” said he, “did he come through this gate or was he only passing it? This dyke, you see, opens into the creek about three-quarters of a mile farther down. The probability is, therefore, that if he came up from the river across the marshes he would be on this side of the ditch and would pass the gate. But we had better try both sides. Let us leave our things by the gate and explore the ground for a few hundred yards, one on either side of the ditch. Which side will you take?”
I elected to take the side nearer the creek, and, having put my camera down by the research-case, climbed over the padlocked gate and began to walk slowly along by the side of the ditch, scanning the ground for foot-prints showing the impression of boot-protectors. At first the surface was far from favourable for imprints of any kind, being, like that immediately around the gate, covered with thick turf. About a hundred and fifty yards down, however, I came upon a heap of worm-casts on which was plainly visible the print of a heel with a clear impression of a kidney-shaped protector such as I had seen in the hut. Thereupon I hailed Thorndyke and, having stuck my stick in the ground beside the heel-print, went back to meet him at the gate.
“This is rather interesting, Jervis,” he remarked, when I had described my find. “The inference seems to be that he came from the creek—unless there is another gate farther down.
Was it common that the bridges of ditches or creeks had guarding gates in 1924?
I've searched for a photo that may show that, but I didn't find anything.