1. ladder (a frame, usually portable, of wood, metal, or rope, used for ascent and descent)
2. scale (an ordered, usually numerical sequence used for measurement, means of assigning a magnitude)
3. scale (a series of notes spanning an octave)
4. ladder, hierarchy (of a company, of the military)
5. scale (the ratio of depicted distance to actual distance)
6. scale (size; scope)

to scale, to climb