In laparoscopic surgery large instruments cannot be used because they cannot pass through trocars which are typically smaller than 12mm in diameter. For example, retracting an internal organ with a slender instrument is often a difficult task. To remove this limitation, we have proposed “assemblable instruments”, that is, parts are inserted through trocars and assembled inside the abdominal cavity to become a large instrument and we have developed assemblable hands. However they use two trocars for assembling, which require positioning and alignment of two assembled parts. This paper presents a simple three fingered hand whose function is limited to retracting. We propose a much simpler assembling method “single trocar assembling” for the hand. Experimental results verify that the hand can be assembled easily and that it can withstand a force of 25N enough to rectract a pancreas.