Abstract: This relates to an attachment kit for an offset printing press of the type manufactured and sold by A. B. Dick Company, which attachment comprises a leveling system including a pair of pivoting boards constructed to be mounted in parallel relation on a base board set on the feed table of the press to support two piles of envelopes in side-by-side relation. The vertical leg of a T-shaped guide bar having its cross bar and spacer fastened to the main bar of the press, passes between the two piles of envelopes and projects into a slot in the base board. A pair of backing plates having vertically-projecting members which bear against the rear of the envelope piles, are constructed to be fastened on opposite sides of the main bar of the printing press. This arrangement enables two piles of envelopes to pass through and be printed simultaneously by the press.