With enough force, any bolt can be a shear pin.

Shear pins are used to hold together parts of a rocket until they are separated by a deployment charge. They help to act against natural pressurization and flight forces pulling apart a rocket before needed. While traditionally, shear pins were pins made of a low-strength plastic, it is much more common to use plastic bolts now. There are two commonly used variants, #4-40 Nylon bolts, and #8-32 Nylon bolts. They can be purchased from any common hardware supplier. \

Shear Pin Positioning

Shear pins should be evenly spaced in a circular pattern around the part that they constrain, You should never use a single shear pin to hold together two parts! A minimum of 3 shear pins is recommended, with 4-5 being the optimal number. 

Shear pins do not need to be a screw-tight fit in their drilled holes, or be captured from the back with a nut. Usually, a touch of hot glue is placed over the top of the shear pin to help keep it constrained to the rocket. For smaller rockets, just the friction force of the hole is enough.

Keep in mind that you must update deployment charge calculations based on the number and size of shear pins being used. Not all calculators compensate for this, so be careful!