A ladder drum for adjusting and regulating the angular orientation and closure of horizontal slats of a venetian blind, of the type incorporating ladder cords or tape ladders, having a polygonal profiled structure comprising a series of planar sidewalls defining a substantially hollow interior. The number of sidewalls defining the polygonal structure is greater than four sidewalls, and less than or equal to twelve sidewalls, with each adjacent plane sidewall having an internal angular orientation in the range of 90° to 150°. To enhance the uniform closure of the slats of a horizontal blind, the polygonal ladder drum is more preferably in the form of an uneven hexagon that is formed from injection molded plastics. The opposing top and bottom sidewalls are greater in dimension than the mediate sidewalls, and have attachment means to insert various widths of ladder tape. The mediate sidewalls have at least two opposing access slots to insert and retain ladder cords in a counter balanced relation.