A kanin was a square sun (a sun = 3.03 cm), but lower class government officials were not allowed to have one of that size and instead, they had to use the seal called "半通印" which was half the size of the original one.
大きさは方寸であったが、下級の官吏の場合は認められず、縦半分に割った大きさの「半通印」と呼ばれる印を使用しなければならなかった。