Chairs with semi-closed back

 

— a kind of middle option between closed and open backs (see relevant paragraphs). The classic version of this design is a plate mounted on a seat using two supports; thus, in the upper part the back is actually closed, in the lower part it is open. However, there are other options: an almost closed back with a narrow horizontal slot, a plate with an ornament of holes, etc. Anyway, such devices combine reliable back support and good ventilation, but they are inferior in comfort to purely closed backs, and in terms of ventilation quality — open.