2001 Volvo S60 Timing belt Cog on crank shaft

I do not understand -- It will need a tap "to get over key"?

A mobile mechanic came out to do a timing belt change, crank and cam seals and water pump. There's a cog/gear the timing belt wraps around. He had that on the crank shaft. The car would not start, he thought it needed to build compression. He left that day to come back the next day and crank it to build compression. He had a stroke that night and has been hospitalized since.

Have another guy helping me trying to pick up where the first guy left off. We noticed the cog/gear was NOT flush to the engine, the nut holding that on bottomed out 1/2 or so - realized that the serpentine wheel was not between the nut and the cog as should of been, possibly thats whay the cog/gear was not flush.

The new mechanic believes the cog/gear should slide by hand to go flush but it doesnt. Are we supposed to tap it home?

We want to know can the cog/gear be lightly tapped flush, the serpentine wheel added and the bolt tightened we think that will solve the problem.

BUT need to know is it correct to tap the cog/gear forward because its not sliding all the way by hand. There is no woodruf key on the shaft. I hope I am being clearer

You have been extremely helpful.

Interfearance engine.
Sadly, the previous mechanic, tried truning the engine with the belt on the cog/gear BUT without
the cog/gear being flush to the engine.

My new guy's best guess is that the slight difference caused by the cog/gear not being flush to the block may equate to the timing being off by 1 or two notches on the belt.

Do you think that's enough to of cause valve damage? Fingers crossed.