The bone mill in Fretter, a protected technical monument, is a remarkable testimony to pre-industrial agriculture and the coal and steel industry. Built around 1900, it was in operation until 1945 and processed 30 to 40 quintals of dried bones into flour in winter. This bone meal was essential for fertilizing fields and as a feed supplement for young cattle and chickens. Its exceptionally long period of operation resulted from the shortage of raw materials and the economic conditions of both world wars and the interwar period.
The technical equipment of the bone mill is particularly noteworthy. The cast-iron stamping mill, a so-called "Californian Poche" from around 1860, is a unit formerly used in mining for crushing ore and slag. Its reuse in a bone mill makes it a rare specimen and a unique reference to the regional coal and steel industry. Driven by an overshot water wheel, this unit demonstrates the efficiency of early engineering. It is one of the few surviving bone mills in Westfalen, and its cast-iron stamping mechanism sets it apart from the comparable models, which are predominantly made of wood. Today, the historical site offers insights into past working worlds on request and for special events.