Always use a reliable stud finder (like the DEWALT DW0150) to scan the area for studs, electrical wiring, and plumbing lines before marking your cut. After marking, make a series of small, shallow pilot holes with a drill or jab saw to visually confirm the cavity is clear before making your main cuts. If you hit an obstruction, stop immediately and reassess.

Install the panel directly over the specific plumbing components you need to access, such as shut-off valves, cleanouts, or fixture P-traps. Choose an area that provides sufficient working room behind the wall once the panel is open. Ideally, select a spot between two studs to avoid cutting structural elements, confirmed with your stud finder.

If the opening is slightly oversized, you can often compensate by applying a thicker bead of construction adhesive (like Loctite Power Grab Express) and caulk around the panel's flange to fill the gap. For larger errors, you might need to patch the drywall with a repair kit and recut, or purchase a slightly larger access panel to cover the mistake. Measure twice, cut once to avoid this common issue.

While a utility knife (like the FASTCAP Triblade) can be used for some straight cuts, a jab saw (such as the Milwaukee Folding Jab Saw) is highly recommended for this project. It provides better leverage and control for cutting through drywall, especially for internal corners and thicker sections, resulting in cleaner and more precise openings.