“Carpenter's gap” above fascia for attic venting. – GreenBuildingAdvisor

Mid-century houses used a “carpenter’s gap” above the eave’s fascia board for the lower attic vent. The asphalt shingles and starter course extend over it to direct rainwater into the gutter and intake air can be induced under the shingle overhang into the attic and out the upper attic vents.

The questions during roofing replacement while keeping the gap and the gutters are:

How can mice and bugs be screened along this gap?

How can the shingles be supported at the necessary overhang?

Does a product exist to support the roofing edge and screen the gap?

Many thanks!