Harden v. t. : To make hard or harder; to make firm or compact; to indurate; as, to harden clay or iron.

Harden v. t. : To accustom by labor or suffering to endure with constancy; to strengthen; to stiffen; to inure; also, to confirm in wickedness or shame; to make unimpressionable.

Harden v. i. : To become hard or harder; to acquire solidity, or more compactness; as, mortar hardens by drying.

Harden v. i. : To become confirmed or strengthened, in either a good or a bad sense.

Example:
What does Harden off seedlings before you planting outdoors mean?

Taxonomy
made furniture, Harden Furniture, American-made, Artistry, solid wood furniture, Luxury, sustainable furniture, Fine furniture, upholstery, go green, WROC-TV, made in America, generation to generation, SFI, SFC, legacy, environmental consciousness, hand-in-hand.

Defination from the web:
... Certified by both SFI® and SFC®, Harden Furniture's enduring legacy of environmental consciousness goes hand-in-hand with its commitment to ...