The four convicts are scheduled to be hanged on January 22.
More than a month before death warrants were issued in the Nirbhaya gang-rape case, a jail in Bihar had been commissioned to make 10 execution ropes which are likely to be used for the four convicts scheduled to be hanged on January 22.
The Buxar Jail, the only prison in the state having the required know-how, had received an instruction to the effect in the first week of December.
The four convicts in the Nirbhaya gangrape and murder case will be hanged on January 22 at 7 am in Tihar Jail, a Delhi court said on Tuesday.
Nirbhaya, a 23-year-old paramedic student, was gangraped and brutalised on the intervening night of December 16-17, 2012, inside a moving bus in south Delhi by the four men, including two others, before being dumped on the road.
She died on December 29, 2012, at Mount Elizabeth Hospital in Singapore.
According to Buxar Jail Superintendent Vijay Kumar Arora, the ropes are "strong" but have a "short shelf life as these are made of unprocessed cotton". They were made available to the prison directorate by the December 14 deadline.
"We do not know where these are going to be used. But, the Buxar Jail has a long tradition of manufacturing such ropes," he had said.
"It is from this jail that the rope used for executing the death sentence awarded to Parliament attack case accused Afzal Guru was sent. In 2016-17, we had received orders from Patiala Jail though we do not know for what specific purpose," he had said.
"It takes about three days to prepare one rope and it involves mainly manual labour with a little use of motorised machinery," he had said.
Mr Arora had said the last time a rope was supplied from here, it had cost Rs 1,725 "only".
The amount varies from time to time mainly on account of fluctuations in prices of iron and brass, he had said. "These metals are used to make bushes fastened around the rope to ensure that the noose remains firm around the neck and the knot does not come undone, when the weight of a human body is suspended from it," the jail superintendent had said.
Asked about the manpower required for the job, he had said five to six persons are usually engaged in making one rope.
"Yarns made of 152 strands of thread each are plaited together to come up with a rope of the desired dimensions. Each rope uses up close to 7,000 such strands," he had said.
The recent sexual assault and murder of a veterinarian in Hyderabad and subsequent killing of the accused in a police encounter, had evoked a fresh clamour - including appeals by family members of the Delhi victim - for the execution of the convicts, whose death sentence was upheld by the Supreme Court more than a year ago.
Incidentally, one of the convicts - Akshay Thakur, who worked as a cleaner on the bus - hails from Aurangabad district in Bihar.