'Plastic end caps' for roofs

[F]

The mortar between the roof tiles and the asbestos undercloak at the gable ends of the roof has suffered over the winter with the outer 4/5mm falling out in some instances. Do the plastic end caps I've seen on a few houses offer any protection against this kind of frost damage?

Anyone able to tell me how they are fixed (the bargeboard is uPVC)?

Do I need to repoint before fixing them?

Do they come in different sizes?

Oh, and what's their correct name (really don't want to go into a suppliers and ask for some plastic end cap thingys for a roof!

TIA

[m1ss_wh1te]

Try Dry Verge thus

[Kipper at sea]

Dry verge. When fitted from new there is no undercloak strip fitted. The tile lath ends protrude over the barge board and the dry verge is fixed into the lath and the bottom of the next one slots into the top of the first and so on. There is a set distance of overhange and there is a specail eave one all come in left and right.hand There are also different sizes for different tiles.