I have heard these markings referred to as "fish scales". Might help some picture them more clearly. I find the bark on red maple flakes off easily whereas the bark on sugar maple is hard to pry off. This is a relative thing so not easy for those who need to compare and can't.
By taking binoculars and looking up at the leaves you can see if the tree is a
red maple: indentations are v-shaped
or a sugar maple: indentations are rounded
This
link can help you see the leaves.