The main advantage of concrete, stone or brick walls (I’m talking about using an existing wall) is that they are already there and don’t require a separate framework. Modular holds can be mounted directly to these walls although there are some disadvantages to this approach. Concrete anchors tend to be expensive, are finicky to work with in contrast to the plywood and T-nut system, and hold breakage and rotation problems are worse on concrete walls. When I talk about concrete walls I am referring to two basic types - solid concrete or stone blocks that make up structures such as a bridge or Hoover Dam (hey there is nothing wrong with dreaming), and hollow concrete block such as found in a typical basement or the side of buildings. For those folks who are determined to make a wall out of a large department of transportation type structure you should take note that there are dozens of concrete anchors available that can anchor holds to this type of solid concrete. For solid concrete or brick (and again don’t do this at the local natural crag) the best anchors to attach modulars are drop-in anchors (or self drives) as these can be used with the existing hardware supplied with most modular holds. Drop-in anchors are also perhaps the least expensive bolts available and make fine, strong lead anchors so they can be used to attach hangers as well. When the top of the concrete wall is not available and you need to aid your way up, drop-in anchors used to make a bolt ladder can later be used to attach modulars as well as provide protection. You should keep this in mind when you are aiding up so you don’t have bolts with limited utility later (i.e., all in a straight line). Other types of bolts are generally less versatile and more expensive so I do not recommend them.

Hollow concrete block (such as your basement) is much more limited in the anchors that will hold modulars and can be a bit of a problem. The only affordable anchors for hollow concrete block are lead shields which are used with lag bolts. These don’t hold up well to repeated use so you won’t be able to change your holds around often. Another problem with lag bolts is that most modulars are designed to be used with allen head bolts and 3/8 inch hex head bolts can’t be tightened because a socket wrench won’t fit into the recess in the modular hold. One solution to this problem is to use 5/16 inch diameter lag bolts which are strong enough and also a bit cheaper. For a reusable hollow-block concrete anchor the best option are double expansion lead shields. These contraptions provide a female thread in the concrete so you can use them with existing bolts. They also exert an overall outward force as you tighten them so you can use them in hollow concrete block or rotten concrete. Unfortunately these anchors are very expensive and you must drill a hole of much greater diameter than the bolt you are using. To minimize these problems you can use these anchors in 1/4 inch bolt size, which requires you to drill a 1/2 inch diameter hole. This diameter hole will just fit in the space occupied by the mortar between blocks. The advantage of this is that you can later remove the shield and fill the hole with mortar so you haven’t done any permanent damage to the wall. You will need to use a 1/4 inch washer between the bolt head and the modular hold but other than that this size anchor is plenty secure. In the long run it may be less expensive and more versatile to bolt 2 x 4’s to a concrete wall with inexpensive lag shields and then attach plywood panels to these with drywall screws. This also enables you to create a wall that is slightly less than vertical or overhanging by using additional 2 x 4’s as spacers.