When using thinner high-strength rope, sometimes you want to pull really hard on the rope, but you can't because being thin, the rope will cut into your skin.

The solution is to attach a handle on the end of the rope. The optimal shape for this handle is a triangle.

The "grip" part of the handle should be thick enough that it spreads out the load across your fingers.

The reason a triangle shape is optimal is that if you draw a vector diagram of the forces on the ends of the grip, they align with the sides of the triangle. The reason the line should attach at the ends of the grip (instead of the middle, like a T-handle) is that this minimizes rubbing against your fingers, even when flailing the handle around in circles — in this configuration, the rope is pretty stable, regardless of lateral forces. When using extremely thin+strong line (ie. Spectra/Dyneema fishing line), you want to avoid rubbing the rope against your skin, because it can cut into your skin.

buy a triangular handle

Commercial triangular-handles are available for these specialized purposes:

construct a triangular handle