叩 is a Chinese hanzi, listed here under the keyword “knock”. It is built from 口 (mouth) and 卩 (seal). It appears as a component in 1 other character in this index.
On KumiJi Glyph Explorer, open the parts search and type “mouth” + “seal”. 叩 is among the results, together with every other character containing the same shapes.
Open 叩 in the interactive kanji search
to expand every part down to its smallest pieces, add your own names and mnemonic stories,
or search for other characters by their parts.