Draw a picture of a ramp.  Draw a vector from the boat perpendicular to the ground.  This represents gravity acting on the boat or the weight of the boat.  Draw a vector perpendicular to the ramp until it meets the other vector.  This vector represents the force holding the boat flat on the ramp.  Label the drawing with the information you have and try to solve the triangle for the vector travelling along the ramp.  This is the one keeping it from sliding down the ramp.