Further information:
In mound no. 35, excavated by Oluf Rygh in 1870, iron keys were found alongside two flat square fittings made of iron. These items were discovered together with burnt bones in a large pile within the burial mound. The iron fittings had uneven rounded holes in the center and indications of nails in the corners, suggesting they are parts of a lock mechanism. However, no box or chest was discovered. 

Both keys are designed with hooks to fit the lock's mechanism. However, the specific type of lock remains unknown. Whether the keys were meant to be twisted, pulled, or pushed cannot be determined. The illustration suggests a mechanical process where a hooked key is maneuvered and pushed into the opening to lift a locking device fitted in a lid.