The most common and most likely answer to this crossword clue is the 9 letter word KNEEHOLES
K
N
E
E
H
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Buddy explains!
The straight part
We know that "Recognize base types" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case recognize base types = kneeholes.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does KNEEHOLES mean?
KNEEHOLES noun- A space for the knees (and lower legs), especially under a desk.