Consider two tiny plane(flat) surfaces A and B meeting at a straight line L.We have a preassigned vector on A at some point P on it.Is it always possible to have a vector parallel to the first one and lying on B at some point on it(say Q)?
[The first vector(that on A) is assumed as not parallel to L]
The two planes may be considered as the adjacent tangent planes on a curved surface over which we are working out parallel transport along some curve lying on it.