of the ditch into the mountain itself. This work was a lot harder—the cost for each cubic metre of blasted tunnel was five times the cost of a cubic metre of blasted ditch—both due to the confined space in the tunnels and the risk of damaging the bedrock. The use of black powder instead of dynamite reduced the risk of bedrock damage, but it also increased the time needed to complete the tunnels. All in all, the amount of bedrock bored, blasted, loaded and transported away from the forts has been estimated to be around . Finishing touches When the ditches and tunnels were finished, concrete works started, including flooring, construction of joist systems in forts with second floors, staircases, partition walls and counterscarp galleries. Water wells were bored to a depth of up to to guarantee water supply, since the forts were supposed to be self-supporting. However, the most demanding part of the project was the construction, transport and installation of the armoured turrets and the armament itself. Two companies had been previously contracted for the construction of other fortifications in Sweden, Swedish AB Bofors-Gullspång and French Compagnie des Forges de Châtillon, offers from both companies existed already in 1901, but it was not until after tests conducted in December 1902 that the Swedish company was contracted and given royal approval on 26 May 1903. The order was for the and pieces that was to be mounted on the first three forts. The following two forts at Rödberget and Mjösjöberget were to have pieces, an order Bofors would get as well, but due to the time factor a few of those were actually delivered by the French company. The cost of a single armoured turret for a 12 cm piece was almost 100,000 kronor—around $800,000 (as of 2011) in today's money—and it could weigh as much as . It was delivered in parts to simplify transport, but the heaviest part still had a weight of . The parts were delivered by rail up to Boden and unloaded with the help of gantry cranes. As the roads of the time could not handle the weight during summer, transport had to wait until winter when the frost had hardened the ground. The turret parts were lifted onto sleighs drawn by 16–30 horses depending on the situation. The toughest stretch, up the mountain, was handled with the help of block and tackle,