Mexican Red Knee Tarantula sexing.

[Glenn]

Do you know any good links on how to do it properly?

I can tell you.
You can soak it up in soapy water, then very carefully unfold the abdomen part and have a look on the inner surface of the abdomen to find a flap in between the first set of book lungs. This way is fastest, but the molt will probably be ruined, and I have a feeling you'll want to preserve the molt for display afterward. If that's the case, then soak up some paper towel with hot soapy water (not so wet that its dripping, but wet enough that it will drip if you squeeze it), and place it in an airtight container like a delicup or plastic Tupperware with the molt on top. Wait a few hours, overnight, or until the molt is nice and soft again, and very carefully open up the abdomen and look for spermathecae. When you are done, pose the molt back to how you want it, and let it air dry.

[Truffs1178]

I can tell you.
You can soak it up in soapy water, then very carefully unfold the abdomen part and have a look on the inner surface of the abdomen to find a flap in between the first set of book lungs. This way is fastest, but the molt will probably be ruined, and I have a feeling you'll want to preserve the molt for display afterward. If that's the case, then soak up some paper towel with hot soapy water (not so wet that its dripping, but wet enough that it will drip if you squeeze it), and place it in an airtight container like a delicup or plastic Tupperware with the molt on top. Wait a few hours, overnight, or until the molt is nice and soft again, and very carefully open up the abdomen and look for spermathecae. When you are done, pose the molt back to how you want it, and let it air dry.

I think I'll just leave it as I want to keep all her sheds the way she left them. Thanks anyway though.

[Truffs1178]

She's about to shed again because the bald spot on her abdomen has gone black. Can't wait to see how big she will be this time. Do you guys use heat mats on your Ts? I just heat the air temp in her terrarium and was wondering what the pros and cons of using heat mats compared with air temp is(if any).