硬 - Stretched HARD as a Rock

Readings & Meanings:

かた（い）

コウ

hard

Common Usage:

硬い

硬派

硬貨

Examples:

その筆は馬の硬い毛を使っている。

彼は硬派な男だ。

硬貨をポケットに入れた。

Translations:

That brush is made from the stiff hairs of a horse.

He's a tough-as-nails guy.

I put the coins in my pocket.

Radical:

Ishi-hen on the left, 石.

更 is the phonetic. You might recognize it from 便利. It's made up of 丙 (a table and two human legs being stretched) and 攴 (alternate form of 攵, hand and stick, action indicator). 更 means to tighten, renew, or stay up late.

Together, they indicate something stretched so tight it's hard as a rock.

Important:

This かたい is just to indicate physical hardness.

The opposite word is 軟, meaning physically soft.

References:

http://www.kanjinetworks.com/indices/radindex.html
http://www.thejapanesepage.com/node/kanji/7.htm