BT BB 164a(11) :אנחנא שהדי על מחקא ושטרא אניירא‏ : we witness on the erasure while the contract is on the (un-erased) paper
See the entire entry for mḥāq, mḥāqā v.n. erasure

BT BB 164a(11) : אנחנא שהדי חתימנא על מחקא ושטרא אניירא‏ : we witnesses have signed over an erasure, but the contract is (written) on a blank section
See the entire entry for nyār, nyārā n.m. paper