Is there a word to describe using one thing as if it is for another purpose? For instance, Chaplin handling his cane as if it's a pool-table cue stick, or someone using a racing hurdle as a clothesline, or a bird using a stick as a fishing pole?
A common usage would be substitute. Chaplin substituted a cane for a pool cue. Clothesline was substituted for the missing hurdle.
The connotation is usually not so light, but for the cane:
misappropriate - to put to a wrong use.
It is more often used in that sense for ideas and not objects.
You could also say it's reappropriation in the case of the clothesline. Appropriate is a verb meaning "to authorize for some specific purpose," so to reappropriate would be to set aside for a new purpose.
Again, reappropriation is not generally used for objects. You hear it used to describe slurs being reconnotated into compliments.
I would not find it out of line, though, to say that the cane is misappropriated and the clothesline is reappropriated.
I think the word you're looking for is repurpose, which means adapt for use in a different purpose.
Source: Oxforddictionaries.com (http://www.oxforddictionaries.com/definition/english/repurpose)
For example, you might say that the bird repurposed the stick to use it as a fishing pole.