Henry and Steve, thanks for the advice. The stair tread project is a replacement of existing treads and risers in a 20-year old home. The existing stair is carpet-covered over 2x12 treads and with 1x8 risers, all of yellow pine. These I will remove, leaving the stringers intact. To replace the treads and maintain the stairway dimensions, I need to have the treads at the same horizons as with the existing stairway, in order to maintain the proportions and match the top and bottom floor levels. Those floor levels will not change. So, if I use premanufactured treads, which have 1-1/16 inch thickness, to replace the 2x12 treads, I thought to use a slab of 1/2-inch BCX plywood as a "spacer" across the stringers. I like the ideas put forth by Steve, and will think about those as a way to maintain the strength of the stairs, while avoiding the fumes and mess of having to finish and varnish the stair treads in place. If you have other suggestions, I am interested to hear from you. The bottom line is that I am trying to devise a method for installing the treads that allows the homeowners to use the stairs more quickly and to avoid the fumes and mess of the typical install of treads, and in-situ staining and varnishing. I could mark the stringer locations on each tread and use a Forstner bit to drill a countersunk hole for stainless steel screws and then cover the screw holes with a prestained plug of the same wood, but that would still leave a visible mark or diffference in wood grain. A darker stained plug would work, if it can be made artistically appealing. Yet, the best of all would be to install the treads with no visible marks. That is the surgical challenge. Again, thanks for the ideas ... and any others that you care to offer.