Although it mostly works as a separate guide on its own, I made it because I thought my guide about organizing the links of the logic gates and triggers is too long, so you can check that guide out first (it teaches you how to use the BEEmod items and how make your maps cleaner with them):
https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=312901555
The other thing is that, well, “AND” gates really are helpful and I’d like to share with you the possibilities of using them. So, I hope you learn something new and get inspired to make more interesting Portal 2 maps!
You can get the “AND” gate here:
BEEmod: http://portal2backstock.com/bee
BEE2: http://portal2backstock.com/bee2/

This segment of the guide is directly copy-pasted from the main guide about logic gates and triggers, so if you’ve read it, you can skip this part.

The “AND” gate is created for test elements which are being triggered by multiple things. However, when you connect multiple activators (e.g. floor buttons) to something (e.g. a laser) the game automatically knows that you want the laser to be triggered only when both buttons are pressed. Therefore, the two ways to connect items, shown in the picture are absolutely the same.
So the only deference is that in-game the logic gate looks ugly?
Yes, kind of, but in my opinion the “AND” gate serves a perfect job as an antline repositioning tool.

As an example I connect a button to a rail platform:
That way the antline chooses the shortest way to the rail, but what if you want the antline to go to the other side of the rail? You connect the button to an “AND” gate and the gate – to the platform:
Change the connection visibility of the platform to none. Then place the logic gate wherever you want on the rail:
And there you have it – the antlines are exactly where you want them to be without using too many light strips or undeployed panels. Or by using only one light strip you can easily make the antlines go around the platform:
…but don’t actually do that, because it gets too confusing. The shortest way to the target is usually the best way.

This can also be used with fizzlers and laser fields:

Sometimes it’s not a good idea to connect something to a timed button which is far from it or when there’s an obstacle between the two.
The player should know how much time he has when he hears that ticking timer sound. The best way to do that is to move the timer close to the button. This is where the logic gate “AND” gets really handy.
Instead of connecting the button to the door, connect the button to the logic gate.
Now the timer is close to the button and can be seen right when the player presses it. All we have to do now is to connect the gate to the exit. And this time we can use a shape to indicate the link.
This way the player knows that the timed button turns something on (or off) for a certain amount of time and that thing is indicated by a square.

In very rare cases you would have to connect a button which is on an “island”, surrounded by water, to something (e.g. a bridge) on another “island” and the shapes wouldn’t be the best way to do so. In these cases just connect the button to the logic gate “AND”, that gate – to another gate, that one – to a third one and the third “AND” gate – to the bridge. Make the links of the second logic gate invisible and place the first and third gates on the edges of both “islands”.
In-game it’ll look something like this:
Note: If you don’t connect the items in that particular order which I described above, it might not work!

Sometimes it’s better to have one thing connected to multiple items via one antline which goes through all those items and ends at the furthest one. This is what I mean:
To do that you only have to connect the activator to the amount of logic gates as the amount of activated items and them – to the items (I treat both glass panels in the screenshot as one item).
Make the links of activator invisible and place every logic gate over the item which is before the item the gate is connected to (it may sound complicated, but just follow the pictures):
If there are two or more items which are the same and are next to each other (like the glass panels in the pictures), use only one logic gate for all of them and leave only one of their links visible!
At the end you should have something like this:

In some custom maps I’ve seen buttons which you can press, but they won’t work until you turn them on by another button. These can be made in the puzzlemaker with the help of, again, “AND” gates! As an example, I’ll show you how to turn on a floor button by pressing a pedestal button:
First you make the floor button’s connections invisible and connect it to an “AND” gate, which you put over the button.
Then you connect a pedestal button to the logic gate and keep the links visible.
Lastly, you connect the gate to whatever item you want, I’ll use the exit door as an example.

Note: If you don’t connect the items in that particular order which I described above, it might not work!

With these examples I provided, expect a little to a lot of trial-and-error experimentation getting your “AND” gates just right. I hope you found this guide useful. Happy map making!

If you have further suggestions, don't be afraid to send a comment my way!
If I find the tip useful, I will put it in the guide!

Feel free to leave a like, just press that 'thumbs up' button. Thanks for reading!