Ee was removing a pin from the rt. front strut of an R85 Haul Truck using a porta-power. The EE placed a 6x6x30 block vertically to act as bracing so the unit would not damage the break rotor. EE took down the unit to compress the ram, and when doing this a gust of wind knocked the block over striking the left thumb. Result was a fractured thumb, splinted and returned to work.