Fortunately, the grading system for aid climbing is standardized worldwide—ranging from A1 to A5 (Australia uses the M0–M8 system, where M stands for mechanical, meaning mechanical equipment). Routes marked with C1–C5 indicate clean aid climbing, where only removable protection like chocks can be used to avoid leaving scars on the rock. Sometimes, clean aid routes also use the A0–A5 system for grading. If a route is graded using the C0–C5 system, it means climbers are expected to respect the established tradition and preserve the route’s natural state as much as possible. In fact, aside from differences in climbing methods and philosophies, the difficulty levels of the C and A systems are essentially identical.

       Unfortunately, there are many interpretations of this standard. Generally, the grade of a particular route often depends on the first recorded ascent.

       Typically, and more traditionally speaking—the grading of aid climbing follows:

       A1: All placements are simple and secure.

       A2: Most placements are fairly secure, but the process is somewhat difficult and awkward.

       A3: Many placements are unreliable, but there are often solid protection points.

       A4: There are individual, consecutive placements that cannot hold body weight.

       A5: Over 20 meters of continuous, mostly unreliable placements.

       In Europe, most aid routes were established a long time ago, and their grades have sometimes been downgraded. Simply put, placing protection at A3 is not very reliable, but can usually withstand short falls. At A4, some placements may only hold body weight, but they rarely occur consecutively. A5 is virtually unheard of. A0 is used to describe routes with permanent, solid protection.

       In the United States, modern equipment and enthusiasm have driven climbers to tackle taller and harder big walls. In just an astonishingly short span of ten years, aid climbing was pushed to its limits. This also led to changes in how grading standards are interpreted. Here's how John Long and John Middendorf explain modern aid climbing grades in their book *Big Wall*:

       A0: Climbing while hanging on gear, stepping on pitons, or pulling on things like chocks to ascend. Ladders aren’t necessarily used, but it’s not considered “free climbing.” Perhaps it could be called “French free climbing.”

       A1: Easy climbing. Placements are simple and solid, each able to hold a fall.

       A2: Moderate climbing. Placements are solid but often difficult to place. There may be one or two unreliable placements above a solid one. Falls are not dangerous.

       A2+: Moderate climbing. There are more unreliable placements above a solid one. Serious falls are possible, but usually not a big deal.

       A3: Hard climbing. Multiple consecutive unreliable placements, each must be tested before weighting. Although there are a few solid placements in each pitch, they are rare and far apart. Falls may cause over eight placements to blow, with some danger involved. It may take hours to complete a pitch.