Service of a kohen who is standing on something other than the floor
Having a separation between the Kohen's foot and the floor of the Temple's Outer Room during the service: Eruvin 104a; Pesachim 65b; Zevachim 24a
Performing kabbalat hadam with something between the kohen's foot and the floor: Zevachim 15b
Having a separation beneath one foot, assisting in support of the Kohen: Shabbat 93b; Zevachim 24a
Standing on a loose stone: Zevachim 24a
