A desealer was a device that could unscramble most locking mechanisms. However, it took some time to do so, and so one needed to be careful not to get caught while the desealer did its work.
Quark wanted to use a desealer to open the doors to the chemist's shop when he and Rom broke in, but Rom had enough technical expertise that he was able to open them quicker. This disturbed Quark, who did not feel that his "idiot" brother could be trusted after seeing such ingenuity. (DS9: "Necessary Evil")