You turn the crank clockwise until reaching 14 or 15 degrees ATDC, then look in the hole to see if the vee is centered. If not, you loosen the IP nuts [four I think, don't forget the one at the back of the pump], then use the handy built in adjuster to rotate the pump until the vee is centered in the window and voila! Pump timing the easy (and less accurate) way. The locking tool just confirms whether you're exactly centered. I think the only way you can bugger things up with the tool is if you forget it's in there and try to turn the engine over--for Pete's sake, please don't do that !!!

Keep in mind that I'm offering this advice to get you out of a pinch, but you really should either get the lock pin or the RIV tool at some point for more accurate timing. That vee can be difficult to see, so use a high powered flashlight and a clean mirror. To avoid parallax perspective you need to view the hole directly above the vee, not at an angle.