In "The Portable Phonography," the books that are inside a hole in the wall next to Dr. Jenkins's bed are the Bible, the complete works of William Shakespeare, Moby Dick, and the Divine Comedy.
Dr. Jenkins puts these books, the last valuable remnants of a recently destroyed civilization, in a hole in a wall along with his portable gramophone. Just before he goes to bed, he seals up the hole with a piece of board and some earth.
On the inside of the bed, next to the wall, he has a comfortable piece of lead piping that he can feel with his hand. One must presume that Dr. Jenkins is using the piece of lead piping as a weapon with which to defend himself against any potential intruders. Jenkins may have his books and his phonograph records, but they cannot protect him any more than they could protect the old civilization from being torn apart by an apocalyptic war.
And so, he must protect himself with whatever weapon comes to hand as he struggles for survival in a cold, desolate world without civilization.