Slide one end into the j channel and nail the far side of the soffit to the wood fascia board using one nail to keep the soffit in place until you install the vinyl fascia.
How to install vinyl siding soffit and fascia.
Since soffit runs perpendicular to the wall you will be cutting many short pieces depending on the width of your overhang.
Using a level make pencil marks on the wall parallel with the lower edge of wood fascia board at the end of each wall.
Certainteed installation guide for vinyl carpentry soffit fascia.
Use the following instructions for vinyl soffit and fascial installation.
These are for reference points.
Measure the distance between the channels.
If the soffit is to turn a corner cut and install j channel to allow 1 4 6 4mm for expansion at each of the adjoining walls and fascia boards.
Subtract inch 6 4 millimeters to allow for expansion.
Most overhangs are 6 or 1.
This video covers installing the fascia and proper nailing.
Determine the preferred method of installing soffit at the fascia board.
Attach an f channel to the bottom outer edge of the fascia board.
When installing j channel at either wall of fascia board nail every 8 to 12 203mm to 305mm.
Cut your soffit pieces.