Land certificate is the proof of ownership of land rights. Moreover, the certificate making must implemented with the successive procedure in accordance with UUPA (Basic Agrari-an Law) within the renewal rules that are always updated by government. The determina-tion and stipulation of appropriate limits with the principle of Contradictoire Delimitatie becomes the main key before implementing the land measurement. Because, without a boundary agreement between the land owners adjacent to the registered land, it will be-come a time bomb in the future, lawsuit could arise which results in re-measurement and even the cancellation of the certificate. This research is normative research type (doctrinal research) with statute approach and conceptual approach. This research focuses to the literature study; data which becomes the research source is secondary data. This will give the answer that the mechanism for determining and stipulation boundaries in land registra-tion has applied the principle of safety, so the land owner get the legal certainty of owner-ship of their rights. The law consequence if the determination and stipulation boundaries in land are not accordance with the fact in the field resulting in the absence of legal cer-tainty for the certificate of land rights. Conclusion and suggestion in this research is in determination and determination of land plot boundaries in order to achieve legal certainty must in accordance with PP (Government Regulation) No. 24 of 1997 and PMNA/KaBPN No.3 (Regulation of the Minister of Agrarian and Spatial Planning/Head of BPN) of 1997. Magetan Regency National Land Agency Office before implementing the measurement activities must be more thoroughly in the process of determination of land plot boundary in order to reaches the law certainty so that it can be accounted for.