Yes, it was a jawbone, literally. In the first book Roland found it at the basement of an old building. The jawbone was a prophetic remains of a demon, so it looked important and the Gunslinger took the jawbone with him just for a case.


There was a hole in the wall now, a hole as big as a coin. He could hear, through the curtain of his own terror, Jake’s pattering feet as the boy ran. Then the spill of sand stopped. The groaning ceased, but there was a sound of steady, labored breathing.
“Who are you?” The gunslinger asked.
No answer.
And in the High Speech, his voice filling with the old thunder of command, Roland demanded: “Who are you, Demon? Speak, if you would speak. My time is short; my hands lose patience.”
“Go slow,” a dragging, clotted voice said from within the wall. And the gunslinger felt the dreamlike terror deepen and grow almost solid. It was the voice of Alice, the woman he had stayed with in the town of Tull. But she was dead; he had seen her go down himself, a bullet hole between her eyes. Fathoms seemed to swim by his eyes, descending. “Go slow past the Drawers, gunslinger. While you travel with the boy, the man in black travels with your soul in his pocket.”
“What do you mean? Speak on!”
But the breathing was gone.
The gunslinger stood for a moment, frozen, and then one of the huge spiders dropped on his arm and scrambled frantically up to his shoulder. With an involuntary grunt he brushed it away and got his feet moving. He did not want
To do it, but custom was strict, inviolable. The dead from the dead, as the old proverb has it; only a corpse may speak. He went to the hole and punched at it. The sandstone crumbled easily at the edges, and with a bare stiffening of muscles, he thrust his hand through the wall.
And touched something solid, with raised and fretted knobs. He drew it out. He held a jawbone, rotted at the far hinge. The teeth leaned this way and that.
“All right,” he said softly. He thrust it rudely into his back pocket and went back up the ladder, carrying the last cans awkwardly. He left the trapdoor open. The sun would get in and kill the spiders.

http://www.fictionbook.ru/author/king_stephen/dark_tower_1_g...

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Note added at 45 mins (2005-04-10 11:38:33 GMT)
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\"felt for a jawbone...\" -- means that Roland put his hand into his back pocket and seized the jawbone to take it out. Imagine you have a pocket or a bag with many things put in, than you put your hand into it and seek for one of things among many. The only sense you may rely upon is your touching feeling.