At (RAF) Flying Training Schools the sorties were (are?) displayed on little plaques in runners on the programme board. As the sorties were completed they were then removed from the board and placed in a pile to one side. Delays were accomplished by sliding the programme plaques to the right; if the board was full, some may 'fall off the programme' (literally) at this point. When all sorties were completed, the plaques were all 'stacked'.
The chairs at my FTS were of the easy-chair (non-stackable) variety.