If you ever tried to walk on a fallen tree log, you understand what the expression means.

VOA: special.2009.06.07

It is easier to fall off the log than to stay on it.

VOA: special.2009.06.07

He lived in the double log cabin on the side of the mountain.

VOA: special.2009.11.14

He sat on a snow-covered log and ate his lunch.

VOA: special.2010.05.01