Reference for Bava Batra 329:5
כי פליגי באתרא דנהיגי בפשוט ומקושר וא"ל עביד לי פשוט ואזל עבד ליה מקושר מר סבר קפידא ומר סבר מראה מקום הוא לו
it is the custom [to use] plain [deeds] and one said to [the scribe]. 'Prepare for me a plain deed', and [the latter] prepared for him a folded [one], the objection [is valid].<span class="x" onmousemove="('comment',' Since the instruction was for the preparation of a deed in accordance with the usage of the country, the scribe's deviation tenders the deed legally invalid. ');"><sup>6</sup></span> [Where it] is the custom [to use] folded [deeds] and one said to [the scribe]. 'Prepare for me a folded deed', and [the latter] prepared for him a plain [one, legal] objection [may be raised.<span class="x" onmousemove="('comment',' Since the instruction was for the preparation of a deed in accordance with the usage of the country, the scribe's deviation tenders the deed legally invalid. ');"><sup>6</sup></span>