There are grooves carved into rock in several places in Europe, and most of them appear on the Swedish island of Gotland. In Sweden, there are also grooves in north-western Scania and Halland, but they have also been found in Tavastia in Finland and in Luxembourg. There is no consensus as to why they were created, but it has been suggested that they were made for sharpening swords, while others believe that they were used for astronomical observations.
3,600 grooves have been discovered on Gotland , of which 700 are in the bedrock of limestone, while the remainder is on c. 800 stones. The grooves are about 50-100 cm long and about 10 cm deep and 10 cm wide.
They began to attract scholarly attention in the 1850s. In the beginning they were called “sharpening stones”, but later they received the name “sword sharpening stones”. After some time, newspapers and scholarly publications began to dispute this since the shape of the grooves made them unfit for sharpening swords. Another reason was the fact that by 1933, more than 500 areas of grooves had been identified on Gotland. They were evenly distributed across the island. It was also noted that they ran in different directions and often crossed each other. There are also picture stones with such grooves which suggests that at least some of them were made during the Viking Age.
During the 1970s, it was suggested that the grooves had been used for astronomical purposes. Priests would have marked the position of the moon at certain dates every 19 years. A problem with the hypothesis was the fact that only very few grooves had been selected to prove the theory.
It has been shown that the grooves on Gotland are not randomly orientated but instead has a large concentration in the east-west direction. And the whole pattern is strongly symmetric around that direction. It has also been shown that the two different groups of grooves, those in the bedrock and those in stones with a large degree of probability has the same variation in directions.
Gantofta is situated 14 km south of Helsingborg and at the location a face of sandstone rock is engraved with thousands of grooves. So far no explanation for their making has been accepted as the plausible explanation. The positions of the grooves suggest that they could have been made with movable wheel constructions. Local tradition on the other hand says they were made by forming the whetting stones, used for whetting scythes by hand.