In a professional kitchen, a lowboy refrigerator or a lowboy oven refers to an appliance residing below the counter or cook surface on the line. Typically lowboy refrigerators can be found below the work surface facing the pass which are designed to hold food at safe temperatures during service and can hold backup mise en place for your reach in on your particular station. Lowboy ovens generally can be found against the wall under the "hot line" of French top ranges, sauté burners, broiler ovens, pasta tank, grills, deep fryers, etc.
it is common to stock lowboy refrigerators with properly labeled quart / pint / cup containers of backup mise en place for service so that ingredients can be quick reloaded without the cooking having to walk off the station. In addition to properly labeled contianers local department of health guidelines will typically dictate that there be thermometers present and that they maintain a temperature below 40 degrees.