Explanation:
28. Such bellows existed in China at least since the 5th century BC, when it was invented, and had reached Europe by the 16th century. A piston is enclosed in a rectangular box with a handle coming out one side. The piston edges are covered with feathers, fur, or soft paper to ensure that it is airtight and lubricated.
23-30. In its simplest form, a hand bellows consists of two flat boards of rectangular, circular, or pear shape, hinged at one end and connected around their edges by a wide band of flexible leather to form an airtight joint.
