Unna's Boot.

This method of compression was developed by the German dermatologist Paul Gerson Unna in 1896. 

A typical Unna's boot consists of a three-layer dressing .

A rolled gauze bandage impregnated with calamine, zinc oxide, glycerin, sorbitol, gelatin, and magnesium aluminum silicate is first applied with graded compression from the forefoot to just below the knee. 

The next layer consists of a 4-in-wide continuous gauze dressing followed by an outer layer of elastic wrap, also applied with graded compression.

 The bandage becomes stiff after drying and the rigidity may aid in preventing edema formation. 

Unna's boot is changed weekly, or sooner if the patient experiences significant drainage from the ulcer bed