Bava Batra 62 - "I am not retaining anything" in Real Estate Contracts

If one sells to his fellow a "house" in a large apartment building, even though he defined the boundaries of the entire building in the deed, it is possible that he intended to sell just one apartment, and he drew the boundaries of the entire building only so that he could utilize known landmarks.  Since the seller stated that he was selling a "house" (as opposed to an "apartment building"), the boundaries written in a deed are regarded as imprecise, and the buyer acquires only one apartment.

Therefore, it is recommended that the seller write some clause such as "I am not retaining anything for myself in this transaction," because with it the seller relinquishes his possible claim that the boundaries he drew were imprecise.