Crafting a witch’s ladder is a way to cast a spell, just like making a jar or drawing a sigil.
They can be used with a specific goal in mind, or simply for meditation, as a healing ritual or a protection amulet.
The first recorded witch ladder found was in an old house in Somerset, England. It was basically a rope with feathers woven into it. You can keep reading about it here: Witches' Ladder: the hidden history
How do Witch’s Ladders Work?
Charms are knotted or braided with specific magical intention into the cords. The number of knots and nature of charms varies with the intended effect.
It is essentially a type of knot magic. At the tying of the last knot, all the energy is directed into the cord and its knots, with a final visualization of the object of the work. The power has been raised and is now ‘stored’ in these knots in the cord.
Witch’s ladders can be used to bind certain energy to use for later. For example for extra strength, patience, or comfort at times. Those energies are stored and when the knots are released, so is the needed energy. 
You could even store your anger or frustration on it during difficult times.
How to Make a Witch’s Ladder
I know @roxanne has made one recently, she wrote a topic on it.
This article also has some interesting information and a guide:
And here’s a Youtube video on how to make one:
