SAC

Path/terrain: Well-constructed footpath. Where possible, all exposed areas are made secure with fixed cables, railings, etc. The risk of falling can largely be ruled out with normal behaviour.
Requirements: No requirements; also possible in trainers. Orientation without any problems, usually also possible without a map.

Path/terrain: Continuous established footpath. Exposed areas made more secure. Partially steep terrain. Risk of falling not ruled out.
Requirements: Surefootedness. Proper hiking boots are recommended. Basic orientation skills. 

Path/terrain: Path not always obvious/visible. The more exposed areas can be secured. You may need your hands for balance. Some exposed areas remain, where there is a risk of falling. Pathless sections over scree or talus.
Requirements: Good balance and surefootedness. Mid/high top hiking boots are recommended. Average orientation skills. Basic alpine experience.

Path/terrain: Occasionally pathless. In certain places you’ll need to use your hands. Some quite exposed terrain, e.g. steep grass slopes, rock ledges, simple firn fields and minor glacier passages (with little crevasse risk).
Requirements: Experience in exposed terrain. Appropriate, sturdy footwear. Good orientation skills. Alpine experience. Good preparation: time and weather considerations, ground conditions & group dynamics need to be considered.

Path/terrain: Often pathless. Individual easy climbing sections. Exposed, challenging terrain, steep cliffs. Bare glaciers and firn slopes which posed some risk of falling.
Requirements: Mountaineering boots. Very good terrain assessment- and orientation skills. Breadth of alpine experience, also in high alpine terrain. Basic skills with ice axe, rope and crampons.

Path/terrain: Mostly pathless. Grade II scrambling. Often very exposed. Terrain examples:
Dangerous talus slopes, rock gullies, steeper sections of snow-free glaciers = increased risk of falling.
Requirements: Excellent orientation skills. Extensive alpine experience and strong familiarity with all technical alpine aids (ice axe, rope, crampons, security devices, etc.).

Source / Further information

Schweizer Alpen‑Club SAC (2023): SAC‑Wanderskala – Definitionen. Alpinmerkblatt des SAC zur Klassifikation der Schwierigkeitsgrade T1–T6 im Berg- und Alpinwandern. - Bern. online: https://www.sac-cas.ch/fileadmin/Ausbildung_und_Wissen/Sicher_unterwegs/Sicher_unterwegs_Wandern/2020_Berg_Alpinwanderskala_EN.pdf. 

Responsibility for the preparation and publication of the SAC difficulty scales lies with the Swiss Alpine Club SAC. The scales are developed, published and regularly revised by the SAC. They describe the fundamental definitions and assessment criteria for various alpine disciplines and serve as an important point of reference for mountaineers as well as for tour planning and training.