Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
pessŭlus, i, m. (neutr. collat. form in plur. pessula, Paul. Nol. Carm. 18, 412) [πάσσαλος], a bolt (ante- and post-class.): occlude sis fores ambobus pessulis, Plaut. Aul. 1, 2, 25: pessuli, heus pessuli, vos saluto, id. Curc. 1, 2, 60: pessulum ostio obdo, shoot the bolt, lock the door, Ter. Eun. 3, 5, 55: foribus, id. Heaut. 2, 3, 37: pessulos inicere, to shoot the bolts, App. M. 3, p. 135, 39; 1, p. 107, 12; p. 108, 24: aperire: pessulum ostii mei aperui dilecto meo, Vulg. Cant. 5, 6.