Recently Litwin and Lomet proposed the Bounded Disorder (BD) file organization which uses a combination of hashing and tree indexing Lomet provided an approximate analysis with a mention of the difficulty involved in exact modeling and analysis. The performance analysis of the method involves solving a classical sequential occupancy problem. We encountered this problem in our attempt to obtain a general model for single access and almost single access retrieval methods developed in the recent years. In this paper, we develop a probability model and present some preliminary results of the exact analysis.