A log in a “jam,” upon which the coherence of the entire mass depends.
1873. Several “drives” often unite; there is generally what is called a “key-log,” and by attaching a rope thereto the whole mass is loosened. Climbing over the “jam,” hunting for this “key-log,” and loosening it, is a most perilous business, as the whole mass often gives away at once, and rolls down into the water in a few minutes.—J. H. Beadle, ‘The Undeveloped West,’ p. 719 (Phila., &c.).
