The Scrambling Grading system puts routes into four categories .
 
Grade 1 :
A rough climb or exposed walk. The occasional hard step where you will certainly be required to use your hands. Route finding will be obvious.
Ropes will only be required by the extremely nervous.
Prime examples in Snowdonia are North ridge of Tryfan and the much traversed Crib Goch near Yr Wyddfa (Snowdon) and Crib Lem on Carnedd Dafydd.

Grade 2 :
The scrambling is more difficult and longer. A rope may be advisable. A broad varied experience of scrambling is required. Route finding can be difficult, and escape from the route, also, may not be easy.
Clogwyn Y Person Arête,Crib Y Ddisgol and Llechog Buttress are fine examples of grade two climbs.

Grade 3 :
More pitches of simple rock climbing on which rope protection is strongly advised, for safety. Dry conditions may be essential. Skills in rope work are required because of lack of escape routes.
Tryfan Bach Approach, Sentries Ridge, Cneifion Arete, Mynydd Mawr and Shark Buttres on Glyder fach

Grade 4
This grade should only be undertaken by the most experienced of scramblers, and donates a particularly serious scramble. This route will contain exposed passages on steep rock or poor vegetation. Routes of this type will require the skill of rock climbing up to a v diff and mountaineering skills where the use of rope and other climbing equipment would be used for passage on key areas. Escape on these routes is difficult and could probably only be escaped from by means of an abseil. Exposure will be high in many parts along the route.
Cyfrwy Arête, Cadair Idris , and the West Peak via Bilberry Terrace on Lliwedd (over 1000 feet of scrambling ascent !)

Winter conditions change everything, snow and ice transform even a grade one climb into a climb of Alpine proportions. Wet conditions can also add a grade to a route.