Those wishing to be doubly sure would make a hand print, and write "freely accepted as certified" alongside, and footprints were even used sometimes, to indicate a contract that there was no running away from.
要再誠信一些的，就蓋上手模，並在旁邊寫著「甘願為憑」，也有人連腳印都蓋上了，這可真是天涯海角都跑不掉了。