All types of cooking involved the direct use of fire. Kitchen stoves did not appear until the 18th century, and cooks had to know how to cook directly over an open fire. Ovens were used, but they were expensive to construct and only existed in fairly large households and bakeries. It was common for a community to have shared ownership of an oven to ensure that the bread baking essential to everyone was made communal rather than private. There were also portable ovens designed to be filled with food and then buried in hot coals, and even larger ones on wheels that were used to sell pies in the streets of medieval towns. But for most people, almost all cooking was done in simple stewpots, since this was the most efficient use of firewood and did not waste precious cooking juices, making potages and stews the most common dishes. Overall, most evidence suggests that medieval dishes had a fairly high fat content, or at least when fat could be afforded. This was considered less of a problem in a time of back-breaking toil, famine, and a greater acceptance—even desirability—of plumpness; only the poor or sick, and devout ascetics, were thin.