机に手をつくは to put one's hands on a desk のように言えます。
Our boss always puts his hands on his desk before he stands up.
「上司はいつも立ち上がる前に机に手をつく。」
My high school English teacher always puts her hands on her desk before she starts to get mad at us.
「私の高校の先生は怒り出すといつも机に手をつく。」
ご参考まで！
カナダ 
