Securing a wall plate

Hmm, after some more reading I'm tempted to ditch the wall plate and use a ledger board instead. Then either:

- the rafters would sit on the ledger (but how to stop rotation?),

- the rafters would sit on a 2x2 fixed to the bottom of the ledger and be skew-nailed into the ledger

- cut a birds mouth that sits on the ledger, and skew nail

- fit hangers to the ledger - the pitch is only 10 degrees.

Any thoughts from those who've trod this way before?

It's normal to use straps to attach to a wall.

A ledger board is normally used for lean-to roof with an existing wall.

Is this what you really mean?

At about 10 degrees for a garage roof, I left gaps in the top course of blocks for the rafters, and used a mortar bed to bring the top of the rafters level with the blocks. Straps with a twist to stop the roof blowing off.

Bed the wall plate and secure with straps

I didn't explain it well. The shed is a lean-to against an existing wall, so there'll be a ledger board at the top end of the rafters. I want a flat top to the framing so the purlins will be on hangers between the rafters. The question is about the bottom of the rafters. I now want the top surface of the rafters to be in-line with the top of the lower wall (so won't use a wall plate). I don't want their ends to be in the wall, so the rafters need to be hung (or supported) below the top of the wall. Hence the plan to use a ledger board and the questions about how best to arrange the connection.

Yes, that would have been simpler but I didn't want the rafter ends to project through the wall

I realise that it's conventional to bed a wall plate on mortar, but why do it if the top of the wall is absolutely flat?

I just would not trust a ledger board fastened to the very top of a (presumed) single skin blockwork outer wall to support a roof.