sleep like a log

If you are sleeping like a log it means that you are sleeping very soundly and is similar to sleeping like a baby. If you are sleeping like a log it means to be sleeping practically motionless as if you were a log. People who sleep like logs are usually always sleeping like that, rather than just on one particular occasion though this can also be used in reference to sleeping like a log because of another reason such as being ill or simply very tired on one particular occasion.