When a German public authority tenders construction work, the work must be specified before anyone bids. The procurement rules for construction, the VOB/A, require the work to be described unambiguously and so exhaustively that all companies understand the description in the same sense. They must be able to calculate their prices safely and without extensive preliminary work. All circumstances that affect the price must be established and stated in the tender documents, for example soil and water conditions. The contractor may not be burdened with an unusual risk.