Apparatus having a drivebox including a motor, a drive connected to the motor, a suitable number of adjustment brackets, and a set of adjustment gussets. A basket is connected to the drivebox through the adjustment brackets and adjustment gussets, and drivebox imparts a sifting motion onto the basket. The basket has a housing, an infeed end, an discharge end, at least one screening deck contained therein, and positioned at a screening deck angle. The apparatus is of a modular design which enables changing the screening deck angle while installed in a facility and without substantial disassembly.