Pins

Pins are also called "grenade pins". They have a ring on one end for pulling them out and for acting as a stop to prevent the pin from sliding in one direction. The other end of the pin has a small springloaded ball that prevents it from sliding out provided the hole holding the pin isn't too large. Use of pins prevents the seat stays from providing lateral support. Without lateral support, the seat attachment has flex and energy is put into flexing the seat frame resulting in inefficiency with respect to other attachment methods. It also requires that seat stays have fixed holes drilled. If the holes are too large, the springloaded ball may not catch and the pin can become dislodged and fall loose -- particularly in rough terrain. Pins often rattle on rough terrain.