1 is quite common to see for me on most doors. If the door is insulated I'll see 2 sometime.

If you have the time check out this site for a good read. This guy is serious about door springs and openers.

Garage Door Torsion Spring Replacement

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I predict future happiness for Americans if they can prevent the government from wasting the labors of the people under the pretense of taking care of them.
Thomas Jefferson