A blank can stand for many letters
During move generation, a blank can represent whichever letter makes a legal word. That means it can unlock words that your visible rack letters cannot make on their own.
A blank is still worth zero points
Flexibility does not mean extra tile value. Once a blank is assigned to a letter in a move, that tile should still contribute zero points. A good solver has to remember which placed letters came from blanks.
Use a question mark in TileSmith
TileSmith uses a question mark to represent a blank tile in the rack editor. If OCR misreads a blank as a normal letter, correct it before scoring so the move generator can explore the right possibilities.
Blanks can create unexpected hooks
Because a blank can become any letter, it is especially useful near existing board tiles. It may create a legal cross word while also completing the main play, which is why board-aware blank handling matters.