Model of a Jeer.Model of a gypsanded two blocks. Each block has two rows of discs that are in a perpendicular surface; Due to the hoist, the blocks are connected in such a way that outer and inner rows of the gig drives run parallel. The outer row of slices of the upper block has five discs, the inner row three, the inner row of the lower block three and the outer row of four. The hoist runs through the upper row of the upper block to the inner row of the lower block, from there and back between the two inner rows, further to the bottom row of the lower block and finally back and forth between the two outer Rows of the blocks. Double grinding of this type were used with mills.