Abstract: A ladder safety apparatus for use with a straight ladder having vertical side rails, and having horizontally aligned openings in the side rails, is disclosed. An example is a hollow-rung metal or aluminum ladder. The safety apparatus includes a flexible metal cable of a length somewhat greater than the rail-to-rail dimension of the ladder, the cable extending through the openings in the side rails. An elongated metal bolt or tube is non-removably attached to each end of the metal cable, to thereby form a linear extension of the metal cable. First and second building attachment means are provided, each such means having a metallic cable-attachment portion with an opening therein whereby the building attachment means is slidably and loosely mounted on the bolt or tube. An adjustment nut or collet is mounted on the bolt or tube, and in a position to adjustably trap the cable-attachment portion on an end of the metal cable. The metal cable includes a protective plastic covering.