Some embodiments of the present invention provide structure that can be installed within a warehouse-type rack to convert the rack for use as a merchandise and display rack. In this manner, warehouse-type racks can be provided with a greater degree of adjustability to accommodate a larger number of shelving and product storage and display configurations. The structure installed within a warehouse-type rack can include secondary uprights connected to secondary front-rear stretchers. Preferably, the connections between the secondary uprights and the secondary front-rear stretchers are adjustable so that the secondary uprights can be secured in different positions within the warehouse-type rack. In some embodiments, the secondary uprights can be secured in different front-rear positions in the rack and/or can be secured in different vertical positions with respect to the secondary front-rear stretchers.