Question: i have a 'baker' coal stove that i bought second hand that has no 'directions with it. i have attached a rough picture of it. my question is there are four knobs on it. two on the damper(used to empty ash tray) door and two smaller ones above that just beneath the glass window. my question is what do the top knobs do? i use the bottom ones to regulate how much air comes in through the bottom to keep the fire cranked... turn it lower etc... do the ones on top also do this with more precision/ Answer: The ones on the top are for secondary air..which is "overfire" air. As you know, coal burns best when most of the air comes from underneath the fire (grate). However, some air above the grate allows the small amount of gases (those blue flames) to be burned off fully. In addition, these upper air controls will work well if and when you burn wood in the unit.