Hi Planks.
45A common letters are every third letter in the first two words. The differing letters are added after the first common letter, one answer is a type of chisel (pl), the other a structural strengthener for ships or planes (pl)
42D common letters are or and bit of t(otty); Barbie is given in TCD as an Aussie term, so one definition has Aussie connection, the other is a Scottish word for a sulk.