A picnic table is a type of table commonly found in public parks, campgrounds, etc. It is usually made out of wooden beams, generally two by fours and is usually 1-3 meters long and 1-1.5 meters wide. Picnic tables can also be made of metal, concrete, etc. Just use your imagination. Below is an ASCII diagram of approximately what a picnic table looks like when viewed from the side.
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And from the front