In general terms, pantrymen worked between the stores and the kitchens and between the kitchens and the table waiters. They were responsible for keeping the kitchens supplied with their raw materials, for making sure that the right dishes and other utensils were available as required, and in working with the kitchen staff to ensure that whatever the waiters needed to deliver to the tables was 'served up' promptly ready for collection.
There was often a specialism involved. One man might be occupied most of the time filling tea and coffee pots, another preparing salads, another slicing bread - or indeed carving meat. In between the hectic mealtimes, an important part of their duty was keeping the pantry clean. Those who were signed on as 'assistants' probably had the lion's share of that task, along with much of the fetching and carrying from the stores.