a bed of nails的用法和样例：
- At any period of history it is the unemployed who find life to be a bed of nails.
- Our marriage has become a bed of nails since my mother-in-law came to live with us.
- With my boss changing his instructions from one day to the next,my job has become a bed of nails.
- The veins on his temples throbbed, and the spring mattress underneath him felt like a bed of nails.
- The machine rests on a bed of concrete.