Construction techniques and design Closeup of Stonehenge from a distance is much speculation has surrounded the engineering feats required to build Stonehenge. Assuming the bluestones were brought from Wales by hand, and not transported by glaciers as Aubrey Burl has claimed, various methods of moving them relying only on timber and rope have been suggested. In a 2001 exercise in experimental archaeology, an attempt was made to transport a large stone along a land and sea route from Wales to Stonehenge. Volunteers pulled it for some miles on a wooden sledge over land, using modern roads and low-friction netting to assist sliding, but once transferred to a replica prehistoric boat, the stone sank in Milford Haven, before it even reached the rough seas of the Bristol Channel.As far as positioning the stones, it has been suggested that timber A-frames were erected to raise the stones, and that teams of people then hauled them upright using ropes. The topmost stones may have been raised up incrementally on timber platforms and slid into place or pushed up ramps. The carpentry-type joints used on the stones imply a people well skilled in woodworking and they could easily have had the knowledge to erect the monument using such methods. In 2003 retired construction worker Wally Wallington demonstrated ingenious techniques based on fundamental principles of levers, fulcrums and counterweights to show that a single man can rotate, walk, lift and tip a ten-ton cast-concrete monolith into an upright position. He is progressing with his plan to construct a simulated Stonehenge comprising of eight uprights and two lintels.Alexander Thom was of the opinion that the site was laid out with the necessary precision using his megalithic yard.The engraved weapons on the sarsens are unique in megalithic art in the British Isles, where more abstract designs were invariably favoured. Similarly, the horseshoe arrangements of stones are unusual in a culture that otherwise arranged stones in circles. The axe motif is, however, common to the peoples of Brittany at the time, and it has been suggested at least two stages of Stonehenge were built under continental influence. This would go some way towards explaining the monument's atypical design, but overall, Stonehenge is still inexplicably unusual in the context of any prehistoric European culture.Estimates of the manpower needed to build Stonehenge put the total effort involved at millions of hours of work. Stonehenge 1 probably needed around 11,000 man-hours of work, Stonehenge 2 around 360,000 and the various parts of Stonehenge 3 may have involved up to 1.75 million hours of work. The working of the stones is estimated to have required around 20 million hours of work using the primitive tools available at the time. Certainly, the will to produce such a site must have been strong, and it is considered that advanced social organisation would have been necessary to build and maintain it.