A grate for a fuel boiler, consisting of plates arranged stepwise or in a cascading fashion, with at least two fixed plates and a movable plate disposed between the two fixed plates. The movable plate is capable of reciprocating to and fro and is provided with an appropriate drive. Combustion air passes through the interspace between the movable and fixed plates and allows for controlled and complete combustion of the fuel. The fixed plates are fastened to a common first holder and the movable plates are fastened to a common second holder. The fastening of each plate to its individual holder is vertically-adjustable. Preferably, the air utilized for combustion of the fuel is only that which has passed through, and preferably been drawn through, the interspace between the movable and fixed plates.