BT BB 3a(50) :ביני אר{כ}<ב>י טפח‏ : between the layers one handbreadth
See the entire entry for ˀwrbtˀ n.f. layer of bricks

BT BB 3a(50) :והני מילי טינא אבל רכסא בעי טפי‏ : this refers to clay, but r-mortar requires more
See the entire entry for rks#2 n.m. mortar (??)