Then using a drywall saw cut along the line you just scored.
Superhydrophobic wall siding leaking water.
Vinyl siding installs in pieces so gaps and overlaps.
If it is a cantilevered area as in this case place your hand at the base of the wall and feel for.
Although vinyl is impervious to water when installed as directed by the manufacturer vinyl siding as a whole is not completely watertight.
Cut a hole in the wall large enough for your head to fit inside.
Wood siding leaks damage.
Ultimately water began to appear on the floor of the kitchen inside.
Water leaks at soffit or eave overhang penetrations for chimneys that permits water to leak at the roof surface then pass behind the siding if the chimney is not properly flashed.
My photo above of ice below some courses of vinyl siding traces a moisture problem traced to improper installation of a through wall vent for a direct vent heating appliance.