Film thread issue with Chinon Sound DS-300 daylight proj.

[ivortripod]

Chinon Sound DS-300 Manual says ' trim leader 3-4mm by using film cutter'. However, the film cutter is missing so how are you meant to trim it?? ok so if the answer is Diagonally [ I can't see how else ! ] , should the longest edge be on the sprocket side or the opposite side ? Driving me mad, all they needed to do was give users a simple line illustration ....
Somebody must be out there with the answer PLEASE !!!!