sketch pad vs sketch block

sketch pad and sketch block both are nouns.

Word	Noun	Adjective	Verb	Adverb
sketch pad	Yes	No	No	No
sketch block	Yes	No	No	No

As nouns, sketch pad and sketch block are synonyms defined as:

sketch pad and sketch block: a book containing sheets of paper on which sketches can be drawn

Other synonyms of sketch pad include sketchbook.

sketch pad (noun)	sketch block (noun)
a book containing sheets of paper on which sketches can be drawn	a book containing sheets of paper on which sketches can be drawn