Note: some call it an ear notch, some call it an ear tip. In all cases, it means the pointed part of the top of the ear has been clipped straight across.

The standard is to clip the ear
right ear notched, female
left ear notched, male

Check around , (try craigslist for example) for rescues near you who do feral cat rescue, also call TNRM (Trap - Neuter - Return - Maintain). They will know:
- the standard in your area
- the low cost programs available
- the requirements - see below what I mean

We have 3 vets in our area who will fix feral cats. Two of them require the cat be in the trap; one of them asks that we transfer the cat to a carrier.
Doing a transfer is tricky with most ferals, and requires TWO people and a closed in space like a small bathroom. Some ferals have learned to come to their caretaker and using a carrier is preferable for those cats. So when I was trapping, it depended on who I caught which vet I wanted to use.

Each of the 3 vets has a different drop off time, although all are early morning. Each has separate pick up times, some as early as 3 PM, some don't start pick ups until 6 PM.

All programs: at the time of being fixed, the cat also gets a rabies shot.

Some programs:

- also test for FIV / Felv ( a positive test means the cat is PTS),
- check for ear mites and administer meds if needed
- apply one dose of flee protection (Frontline or some such)
- check for and remove any tics

There may be different things for your part of the country compared to mine.

You said "I have to catch the cat," but if the ear is already tipped, WHY? do you have to catch that one?

And, AHEM! catching only the girls is a nice idea, but the males do roam, ya know? They can be trapped and fixed as well. You can't a trap to "catch girls only." If you've put the male through the stress of being trapped, may as well fix him; plus, often you can't tell the sex while the cat is in the trap, ferals don't like to allow you to "see back there!"