Before nailing the sill into place when installing a sliding glass door frame, it is recommended to apply what?

Applying a bead of sealing compound before nailing the sill into place when installing a sliding glass door frame is essential for ensuring a proper weather seal. The sealing compound serves to fill any gaps between the sill and the substrate, preventing water infiltration and air leaks that could compromise the integrity of the installation. This is particularly important in areas exposed to moisture or varying weather conditions, as it protects against potential rot and enhances energy efficiency.

While painting and caulking can offer some protection, they do not provide the specific weatherproofing needed at the install point, and plywood, though it may add physical support, does not serve the same sealing function that a sealing compound does. Thus, using a bead of sealing compound is the most effective option for achieving a long-lasting and watertight installation.