Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
oppango (obp-), pēgi, pactum, 3, v. a. [ob-pango], to fasten or fix on, to affix (anteclass. and in post-Aug. prose): ubi savium oppegit, fugit, imprinted, Plaut. Curc. 1, 1, 60: repagula, quae … ex contrario oppanguntur, Paul. ex Fest. s. v. repagula, p. 281 Müll.