可簽的地方蠻多的。比如:

別人申請英國護照/國籍，有一項是ask witness to testify的，你就可以簽；

讓我想想，還可以在Copy件上( such as marriage certificate, birth certificate)簽名,證實這是原件的copy, and還有你認識此人，etc.

I used to sign quite a few for my colleagues when I was working.