A device (10) for blocking workpieces comprises an aligning station (11), which has a workpiece support (12), for aligning a workpiece laid on same, a block station (13) comprising a block piece mount (14), in which block station the aligned workpiece can be blocked by means of a block material on a block piece, which can be mounted in the block piece mount in a centred manner in relation to a substantially vertically extending blocking axis (V), and a workpiece carriage (16) which carries a holding head (15) for the workpiece and which is suitably guided and driven, by means of which workpiece carriage the workpiece held on the holding head can be transported from the aligning station to the block station, can be positioned along the blocking axis in a defined manner relative to the block piece held in the block piece mount and can be held between workpiece and block piece during blocking in the defined relative position to the block piece by leaving a gap between block material and mount. In this way, the aligning station can be moved from a resting position, in which same does not prevent movements of the workpiece carriage, into a working position, in which the workpiece support is centred with respect to the blocking axis, and vice versa.