Cord lock for venetian blinds

Abstract From the Canadian patent

A cord lock for locking a venetian blind in its raised position only. The lock has a housing with spaced side walls spanned by a smooth-surface pin, a knurled roller slidably received in slots in the side walls, a plastic lever below the pin and roller and having an extension below the blind head. The lift cords of the blind pass between the pin and roller. The extension is engaged by the top-most slat of the blind which lifts the lever and knurled roller thereby causing the lift cords to draw the knurled roller up the slot locking the lift cords between the roller and pin.