In feudal times, palanquin and coffin carries worked on pairs. The responsibility for lifting and transporting was equally divided. To shoulder one’s end of the pole means to hold up one’s end of the operation, taking full responsibility for being an equal partner.
(Style: spoken/A=casual male, B=formal male)
A: Iyaa, ano jiken wa jinjika no Yamada-san ga kataboo o katsuida rashii yo.
B: Yappari soo na n desu ka. Maa, Kawai-san hitori de, anna daisoreta koto o keikaku suru hazu wa nai to omottemashita ga ne.
A: Well, it appears that Mr. Yamada from the personnel department had a hand in that affair.
B: Just as I guessed. I figured that Mr. Kawai couldn’t possibly have come up with such an ingenious plan all by himself.