1995 4.0L Explorer Camshaft Position Sensor Replacement

[Peterand]

We bought a new/rebuilt engine from Ford. I pulled out the CPS out of the old engine without noticing that there is a little window on the top of the CPS that shows it's position. We have the engine at TDC 0....but the manual only talks about another tool that we need to purchase in order to install this CPS. Do we really need the tool? As the little window has a couple of lines on it that appear like position marks and a rotation arrow. We are ready to put it back in and I am trying to teach my son some mechanics, but this one has us stumped. Anyone out there can point me to the right direction? Thanks! Peter