Abstract: An adjustable guide assembly for mounting on the upper edge of a longitudinal retaining wall defining a cargo container well of a well car adapted for accommodating containers of different widths in the well, has a base member and a rockable guide member. The guide member has a narrow-container stabilizer surface, a narrow-container loading assistance cam surface, and a wide-container loading assistance cam surface, which are selectively operative by swingably positioning the guide member relative to the base member.