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.
Measure the distance between the channels.
Use the following instructions for vinyl soffit and fascial installation.
Cut the soffit panels to the measured size.
Cut your soffit pieces.
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.
Attach an f channel to the bottom outer edge of the fascia board.
Determine the preferred method of installing soffit at the fascia board.
When installing j channel at either wall of fascia board nail every 8 to 12 203mm to 305mm.
These are for reference points.
Place the soffit panels in the channel slots so that the panels meet.
Subtract inch 6 4 millimeters to allow for expansion.
Certainteed installation guide for vinyl carpentry soffit fascia.
Using a level make pencil marks on the wall parallel with the lower edge of wood fascia board at the end of each wall.
This video covers installing the fascia and proper nailing.