PTŠab 11.b:62[2] :תמן הוא עבד חף {כ}<ב>לוט‏ : there he makes חף (v. MKel 14:8) a tooth of a key
See the entire entry for blwṭ#2 n.m. tooth of 'elbow' key

PTŠab 11.b:62[2] :מהו חף סרגיד‏ : what is חף? a סרגיד
See the entire entry for srgyd n.m. tooth of an 'elbow' lock