It is the mid 1980s and artificial climbing holds are being thought of and created. So now that a few holds are made, the question is:

“How does the climbing hold get attached to the wall?"

At this time there was no standard developed so hold creators were using glue, or a variety of screws or bolts to attach the holds to the walls. Powroll The Wall was offering carriage bolts with wing nuts to attach their block holds to the walls. Entre Prises, Metolius, and Vertical Concepts made their first holds having a wide area on the hold designed already into the hold that will accommodate a variety of bolt possibilities. The bolt holes on the holds were created large to accommodate a socket wrench to be able to tighten a hex bolt.
Entre Prises
Metolius
Vertical Concepts
Franklin
I am not sure when the T-Nut was first created, but the t-nut was not a thought until the later 1980s when the cap screw bolt or button head bolt was brought into the system. So early rock gyms had climbing challenges created, but they were single routes that ascended walls that had holes cut into the walls used as holds or had whatever worked being bolted to the wall to create routes. But yet the wall was simply blank,  and was not pre-made having a thousand  or so nut placements already available so the routes could be easily changed.
late 1980's Course Setters cart
Early 2025 Course Setters cart
Vertical Club, Photo from:
January 1988 story in Rock & Ice magazine
ALTA Bouldering gym
- Joey Whitehead, 2023
Eventually the 3/8” Cap screw bolt which uses a hex Allen wrench to tighten the bolt became the standard. The holds were now created with only having a small round hole which tightly fitted the 3/8 cap screw bolt, and now the bolt hole area was not allowing extra space for a thumb or finger to be used as a additional hold advantage in being able to hold the hold. Even in the beginning of the 1990s, some hold manufacturers were still using a large bolt hole still allowing a socket wrench to be used to tighten the bolt. Example: Franklin Holds, and Climbing Dynamics, etc. Now fast forward to 2025, the 3/8 Cap Screw Bolt is the Standard in the industry worldwide, (Europe is metric equivalent).
And yes ...... The T-Nut is discovered!!!
Hammer in style T-nut
Screw in style T-nut
These are great for volumes!
Industrial 1" steel T-nut.
The t-nut is created with a hex fitment so if a spinning climbing hold was to get cross-threaded stuck, one person could be behind the climbing wall holding the T-nut locked while the other person removes the mangled bolt from the front. The T-nut can be tapped (re-threaded).
3/8 Cap Screw bolt
3/8 Button Head bolt
The early rock gyms created a climbing experience for their customers, but did not really have any routes marked by hold color or identified with tape. Customers would go to the gym and the challenge was to climb that wall, or that other wall, because not one wall had many routes on it. For the June 1988 Snowbird Championship, the Finals route was named the "Lacerator." After the Championship was completed the Snowbird wall was not filled in with any other routes, and the Lacerator became a destination route, that is if the Snowbird hotel was even allowing climbers to climb the route. Eventually climbing holds were being created being multi colored because they looked super cool. Colored tape became the way of identifying the chosen holds that are on each specific route.
Tape rolls - Duct tape
Tape rolls - Gaffers tape
Duct tape was available in most local stores but in Arizona the longer the duct tape is stuck to the wall, the more sticky the tape becomes where eventually it leaves the sticky tape residue on the climbing walls. Gaffers tape became the best choice tape to use in most of the rock gyms. Tape overall has always been a problem since if the piece of tape falls off of a route, then the route becomes that much more of a challenge to climb and can be frustrating to gym customers. Gaffers tape is available in many thicknesses and colors, where at the Phoenix Rock Gym the 2" tape is most preferred to be used. The next major change at the rock gyms is in the 2000's when the color of the climbing holds now determined what holds to use on routes. The routes are now "monochromtic." Tape started to become phased out of the gyms which saves on constant maintenance, and cost. The companies that supplied the tape were making good coin as gym after gym opened across the country seeking their many tape colors. The tape was even available pre-marked with circles, stars, hearts etc. As the tape sales then fell because of the new monocromatic setting system, the tape with the patterns were discontinued, and overall the gaffers tape colors became limited.
Phoenix Rock Gym - Routes follow tape color
Rocks & Ropes gym - Tucson AZ - Routes follow hold color
The rock gyms that were already in business had now to repurchase an abundance of climbing holds all being made in only single colors. The switch over process seemed simple, but in the beginning the course setters missed their mark by still loading the walls with as many routes as possible, but this time not using tape. So climbing customers experienced having to create a new method of navigating through the over abundance of color holds, which at times became confusing. The tape on the old route ID method could have artwork drawn onto it to make following the intended route more easy. People that are color blind were the first to bring forward complaints of the monocromatic routes becoming more difficult to follow. Then over the next few years the climbing gyms had less and less routes created, to allow gaps between the routes so the overall public would have a easier time staying on the intended route. The climbing hold manufacturers developed a standard color holds chart/guide to be used throughout the industry. This made it easier for gyms to keep their different hold colors most separate from each other. At the Phoenix Rock Gym we still love using the route tape ID system. For example: On our overhang TR wall, we presently have 12 routes on it. A monocromatic gym would only set 3 routes on that same wall. Long live the tape!!!
Climbing hold molds from Three Ball Climbing, Tempe, AZ