Distance between nails

[BMAD]

A thin four-foot long chain is suspended by its ends and nailed to a wall.  Both nails are level with one another and parallel to the floor.  Because of gravity, the middle of the chain is hangs down towards the floor.  If the vertical length of the chain is two feet, what is the distance between the nails?

[bonanova]

 

Spoiler

Well I set up the equation for a catenary and found the solution to have a denominator term that was zero. Then I reread the puzzle and slapped my forehead.

Spoiler

It's zero.

 

[Donald Cartmill]

Spoiler

Nails are side by side

 

Edited January 4, 2018 by bonanova
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[CaptainEd]

Bonanova, I see your point (forehead slap echo). BMAD fooled us.