shorten a piece of pine on one side (Hanover BN2)

Hoping someone can help. I need to shorten a piece of wood by about 7cm on one side but I have no tools and I suspect if I bought a handsaw I would end up with a very wonky and rough on one side piece of wood. Hoping someone can assist. The wood is pine and 50 in height and about 1.5 cm thick.