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To permanently secure the new stair treads, first apply an adhesive like liquid nails to the stair stringers (the support beams) where the tread will rest. Use a caulk gun to apply an even bead of the adhesive. Then, carefully place the new tread onto the stringers, ensuring it is flush and properly aligned. Finally, use a nail gun to fasten the tread securely by driving nails into the sides of the stair structure, typically into the stringers and risers, creating a strong bond.