The preparation of a series of entries for inclusion in a subject catalogue or in a printed index is known as indexing. An entry is a basic unit of a subject catalogue or an index. It consists of (a) a means of identifying an item in, or a concept derived from the collection (i.e. the documents of a particular library), and (b) a means of locating the item or material relating to the concept. Indexing is a technique for providing service operation and an index or a subject catalogue is a tool. It is a means to an end, never an end in itself. In other words, it is a communication link between a collection (of a library) and those who intend to obtain some information from it. The process of indexing calls for sensitivity to users' approaches, intuition to select appropriate terms and skill to identify the terms and their relationship, on the part of the indexer. The indexing process also requires the creation and recognition of pattern and rule conscientious and adherence to them, as also accuracy and precision. In other words, the process involves the application of a model indexing system.