Creating silicone molds for climbing holds involves several steps to ensure a precise and durable result. Here's a basic step-by-step guide:

Steps:

1. Create a Prototype: Start with a climbing hold prototype. This can be sculpted from clay or carved from foam. Ensure that the prototype has the desired texture and features.

2. Build a Mold Box: Construct a mold box around the climbing hold prototype. The box should be larger than the prototype to allow space for the silicone mold. Use materials like wood or plastic to create a containment structure.  Seal the bottom of the box on the outside so that it does not leak.  Ensure the surface is level.

3. Prepare the Prototype:  Attach to the bottom of the box so that it does not move and if you used foam; float up to the surface when covered in silicone.

4. Mix and Pour Silicone Rubber: Measure the required amount of silicone rubber according to the manufacturer's instructions. Mix the components thoroughly in a container, ensuring that there are no air bubbles. Pour the silicone rubber mixture over the climbing hold prototype within the mold box.

5. Degassing (Optional): If you have access to a vacuum chamber, degas the silicone rubber mixture to remove any trapped air bubbles. This step ensures a smoother and more accurate mold.

6. Curing: Allow the silicone rubber to cure according to the manufacturer's recommendations. This process typically can take minutes to hours.  Ensure that the mold is kept in a stable position to prevent deformities during curing.

7. Remove Mold Box and Prototype: Once the silicone rubber has fully cured, carefully remove the mold box. Gently separate the silicone mold from the climbing hold prototype.  If a foam prototype was used you can expect it to be destroyed during this process.   Clean out your new mold and it is uready to be cast with your chosen material.