It is a hopeless task. Though Mr Nabi and his friends may eventually clear this blockage they will never clear the road. More than a thousand men are deployed by the Pakistani army to do just that and they are never successful. In a Sisyphean effort they end up pushing boulders off the road only to see them roll down again somewhere else.
The reason for the Dantesque nature of Mr Nabi's labours are straightforward. For most of the Karakoram Highway's length it follows the young river Indus. Loaded with rocks and silt, the water batters its way through the Western Himalayas carving out a deep and unstable gorge as it sets off on its journey towards the Arabian Sea. The river undercuts the base of the mountains through which it cuts its course and, inevitably, they topple forward into the river. The Karakoram are the steepest and nastiest of all the various mountain ranges that make up the Himalayas and its landslides are as bad as they come
This year has been atrocious. The road was blocked throughout most of February and March by rockfalls in its southern section. Just when they had been cleared away news came in of another series of massive slides further north. So the earthmovers and the diggers and the hundreds of pairs of hands - the latter paid all of 4,000 rupees (pounds 55) per month - were redeployed.
The repairs are the responsibility of the Frontier Works Organisation (FWO) which is part of the Pakistani army. They take enormous pride in their work and often paint the roadside rocks with their unit's title, crest and silly nicknames. Yet they are right to be proud. When the highway was built - between 1966 and 1978 - 450 workers died. It is still dangerous work and plaintive roadside memorials list the shahedin (martyrs) who died in the course of their duties.
Working on the "KKH" as it is known is a plum posting for the ambitious. "It's seen as a testing ground," said one senior FWO officer. "Sometimes the weather is so bad that even survival is an achievement."
It isn't all that safe for the users of the road either. All those who live along its length have stories of trucks or buses which disappeared when stretches of tarmac, weakened by the rain, simply gave way under their weight and dropped them into the Indus.
One hotel manager in Skardu told me he was haunted by the sight of 17 corpses being dug out of a landslide that he had watched crash across the road yards in front of his own vehicle. "It was amazing. One moment we were driving along, the next there was a wall of rock and mud in front of us and under it was a bus," he said
The KKH ends, at least heading south, not with a bang but with a whimper. Suddenly the dry, dusty gorges give way to pretty pine forests. The skies are blue and the trees a deep shade of green.
The road sweeps down to the town of Abbotabad where the whitewashed barracks with their polished artillery pieces look genteel and respectable in contrast to what has gone before. Just south of the town of Havelian the KHW officially ends at a long bridge over a dry river bed.