Can I connect a 3 way switch to be used as a single pole? I accidentally purchased a couple of them and only need to control one light each.
Yes, you can use 3-way (UK: 2-way) as 2-way (UK: 1-way) switches. It will work fine. Simply make sure the screws are different colors; you want the common terminal and one of the messengers; not both messengers.
You can do the same with a 4-way (UK: the kind that goes between two 2-ways), again choose screws of different colors, i.e. one from the upstream "side" and one from the downstream "side". They are not necessarily on the same physical side.
Yes it can work. 3-way switches are spdt (single pole double throw) with 3 screw terminals, and regular switches are spst (single pole single throw) with 2 screw terminals.
Just pick the correct two contacts and you are good to go. .
If there are two on one side and just one on the other, then connect to the one that is alone on one side, and either of the other two on the other side.
A multimeter is the quick way to figure out which terminals to use. Just set it for ohms and you will be able to tell what happens as you toggle the switch.
You will have two Common screws. They will be across from each other on the switch. If you look at the switch it will identify both of them it will say common and there will be an arrow pointing to them. Then above one of the common screws you will have another screw. Wire the hot feed coming in to the common on the same side of the switch as the screw which is above. Then wire the hot feed going to the fixture to that screw that is on the same side as the common you just wired in. Twist your bear grounds together and hook them to the green screw. The reason this works and is okay is because as a single pole switch has two screws on the same side of the switch. All you're doing is eliminating one of the commons that the traveler would go to. It is not dangerous for this reason.