Abstract: An insert, or gasket, intended to be used at a joint between two panels. The insert is preferably pre-formed into a particular cross-sectional shape such that it can be easily, and securely, installed between two panels. Preferably, the insert is shaped, in cross-section, with one flange on each end, such that upon installation, one flange is seated on the front side of the panels and the other flange is seated on the rear side of the panels. In the preferred embodiment, the first and second flange portions may include a pair of lips, and the lip of the second flange portion is of a thickness that is greater than that of the lip of the first flange portion. Such a configuration facilitates installation. The present invention also relates to a method of installing such an insert.