A balloon attaching jig is constituted by a ring member and a pair of nail members. The scrubber attachment is constructed by an elongated piece of a foam rubber wrapper in an elongated mesh netting. The method includes the operation steps of stretching the aprons by application of tension via a tension component and, while the fiber drafting operation continues, the bearing unit carrying the aprons being shifted in the horizontal plane in certain intervals. The comparison processing is performed on pairs of every other point of oversampled data. Next, the system performs a timing analysis by tracing paths through a timing graph for the circuit block.