The most highly regarded secret of the largest door manufacturers in the United States is that their most high-end doors have Sing Core inside.


These are among the most profitable privately held companies in the country, and there was a time when they avoided taking on the hard jobs; those jobs that included large doors over 7 ft tall. Why? Because of customer complaints and returns. They were better off excluding that part of the job, and let the individual millworks fight over trying to deliver those big doors.

Then, the millwork that won the job would have to deal with the complaints of having to replace or continually service large oversized doors that were bound to warp and fail periodically over the life of the door.

That is, until these dominant door manufactures learned the true secret; that Sing Core empowers them to create the high-end doors which allowed them to expand and evolve into even more profitable door companies in the USA.


Because they could now provide the largest and most unique door creations with the highest precision (+/- .006-in) and the best guarantee, bar none, thanks to inventor Peter Sing’s patented and patent pending large door building technologies.

50-Year Guarantee

Whether they pass the guarantee onto their end users or not (as their company policy might be only to provide a 1-year guarantee, if any at all, as large doors are normally exempt from any guarantee) the resulting doors with Sing’s core inside are guaranteed for 50-years.

For fifty years they are guaranteed not to warp, bend, twist, delaminate, or otherwise fail for 50 years.

Zero Complaints

For many years, these companies who use this highly guarded secret, they have not had a single complaint, completely eliminating rejects, returns, and replacement doors, all because when necessary, they make sure their high-end doors have Sing Core inside.

We have been told that before Sing Core they constantly had complaints and recalls for these specialized large doors because they would fail due to warping or door or structure being compromised due to materials used or heavy weight.

The reason?

Sing Core is the only way to do it (that’s what they say) and they are backed by the best guarantee in the door industry without fail.

So, we highly recommend that you look into this if you would like to be counted among the best high end millworks and door companies.

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Secrets of high-end door building photos