Abstract: A bed foundation may be retrofitted or otherwise converted in the field to include one or more additional function. In one illustrative embodiment, the bed foundation may be retrofitted or otherwise converted by incorporating a drop-in articulation unit. Such an articulation unit may permit a user to raise and/or lower the head of their bed. In some cases, a second articulation unit may be placed at the foot of a bed foundation to permit the user to independently raise and/or lower the head and the foot of their bed. In other illustrative embodiments, drop-in units may add other functions to existing bed foundations. In some cases, the bed foundation and/or drop-in units may be configured such that it can be easily shipped and assembled in the field by a user.