No, BB, 'not many people know that' 
. That's partly why spelling is so badly taught in many schools.
Right, my 'b'/'d' strategy. Might not work but well worth trying. When written it looks more complex than it really is.
Based on the mouth shapes made when saying the sounds 'b' & 'd'. Also the rule that letters are always written from L to R.
Get the child to say /b/ (sound, of course, not letter name). Ask them what their mouth does when saying it. they should tell you that it starts with mouth shut, then open. So, when writing it start with the straight line (mouth shut) then the 'ball' (mouth open)
Do the same thing with /d/. This starts with open mouth, so 'ball' first. Sadly it doesn't finish with a closed mouth (straight line) but by then the only bit left to write is the upright stroke.
This works for reading too if the confusion happens in reading. When you see the straight line first, shut your mouth for a /b/. Ball first, open mouth for a /d/.
Get the child to write the letter corectly, while saying its sound , as many times as they will bear; do this daily, focussing on one letter only until they can write it automatically in response to the sound (muscle memory in play here). Then repeat with the other one.