Center and level the first section after you install the brackets. The door must be level even if the floor isn’t, so use shims under the section to level it. The rubber gasket on the bottom section will fill the gaps created by an unlevel floor. To hold the level in place, tape it to the section. To hold the section in place, lightly toenail a 16d nail into the frame and bend it over the section. Add brackets and rollers before setting them in place and stack one section on top of another, toenailing as you go up.
The deluxe-model upsell trick: Don't you want the best? Don't you want to protect your family? Galvanized springs may be offered to you at extra expense as "longer lasting". Although bare springs (also called "oil tempered") can develop a light film of rust, the eventual failure is due to fatigue and not corrosion. The use of coated springs (whether galvanized, painted, powder-coated, or surface-converted) is mostly about appearance: the customer likes his new door to look shiny, and the customer doesn't like repair parts that show superficial rust from storage.
The optician's trick: The serviceman looks over your door with lots of scowling, chin-scratching, and tsk-tsking. You ask, "how much?" He replies with the fair price. If you don't flinch at that price, he says, "for the parts", while quoting a large additional cost for the labor. If you still don't flinch, he adds, "each," while pointing back and forth to your pair of springs. (I hope none of you service people are reading this!) I call this the "optician's trick" after the old vaudeville joke about lenses, frames, and left/right.

Had a quick response to my call. thought I might have to wait a couple of days to coordinate their schedule and mine. To my surprise I received service in one and one half hours. Not only that but there was no sales call, technician Mike was fully prepared to give me a quote and complete the work as his vehicle carried everything needed. He very efficiently completed the work and cleaned up after I selected from the options. He replaced the springs all rollers and made needed adjustments expeditiously. I would recommend this firm to anyone needing garage door more
Install the stiffening strut on top of the top section of steel doors with the section lying flat. Then install the opener bracket that replaces the center bracket between the top two sections. While you’re working on the sections, protect them from scratches by putting carpet scraps on top of your sawhorses. Now, slide the rollers into the roller brackets.

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