We present a memory-based planning model. The key component in the memory of the system is the collection of different skeletons of plan operators. A packaging hierarchy plays the key role in construction of a skeleton. A skeleton itself is made up of hierarchically organized plan operators and corresponds to a class of plans. This approach of memory organization differs from existing case-based approaches in which an indexing hierarchy plays the key role in organizing the plans in memory. Modification knowledge plays an important role in plan construction and is distributed over plan operators. A plan is created in a hierarchical fashion by activating the suitable skeleton and performing appropriate modifications during expansion. The model has been implemented in the domain of cooking vegetables.