HERP HELP
Determining the sexes of snakes using a probe Before explaining how the probing procedure is achieved, I thought I should first explain here how the tail structure differs between the two sexes and for those of you who do not know this difference this will give you a much clearer understanding of why the probing procedure works.   Male snakes have a pair of sexual organs that are called the hemipenes. Each hemipenis  is situated inside its own tubular sheath or cavity that is found underneath and inside the tail of the snake. This tubular cavity runs from the tail vent, towards the end of the tail to a distinct of approximately twelve subcaudal scales. The female also have two tubular cavities inside the ventral section of their tail like a male but it does not have any sexual organs there. Because of this, the cavity is only slight, with an approximate cavity depth of about 3 to 5 subcaudal scales. Because of these distinct differences in depth between both sexes, the use of a probe inserted into these cavities to gauge this depth is ideal. Probing would have to be the most commonest method used today to determine the different sexes of snakes. I have always found that although snakes don't seem to enjoy the actions of probing their stress is short lived and with practice can be done very quickly without any dramas. When I have resorted to probing I find it quick and easy to place the subject in to a cloth bag or pillow slip and then only allow the back end of the snake to protrude.
Usually you can secure the snake with your left hand (see diagram 1) while holding the entrance of the bag screwed up against the snake's body preventing its escape. And with your right hand insert a lubricated the probe making sure that the tail is held either straight or bent slightly upwards. I find that if you roll the probe both directions it can cause the probe to go in easier.
Some of the dangers of probing as any experienced keeper will tell you is the possibility of pushing the probe in too far and perforating the membrane at the end. This could end up causing injury and also you may think that you have a male when in fact you have the opposite. If you feel any resistance with the probe you should not continue. Another point is you must probe both sides as there have been cases of people probing one side only and determining it to be a female when in fact it has turned out to be a male with a blocked duct. But to find two sides partially blocked would probably be rare. It is also important not to use a probe that is too small. It is harder to accidentally perforate the end if the probe is a neater fit. You can on occasions determine males by observing their skin sheds. Although male's snakes don't always shed their hemipenes in every shed cycle, they will eventually. I have read most snakes show these in their shed once every three to four sheds but I have never actually bothered to take too much consistent notice. There are other methods used besides probing to determine sex and one method is known as popping. I have not covered this practice here as this is a practice normally only done with snakes that have only just been born or only a few days old.
Determining the sexes of snakes without probe Besides probing you can sex your snakes by visual examination of the tail area. This is a method that I prefer and fully recommend.   You need to hold your snake horizontally in front of you and examine the area around the fifth subcaudal scale. If it happens to be a female then the tail should taper away from the anal area fairly evenly and often quite sharply at first (see diagram 2 ). If you have a male you should notice a slight bulge at about the fifth subcaudal indicating the presence of hemipenes (see diagram 3 ). This method of determining sexes does take a bit of getting used to but with a bit of practice you will find that you gain an eye for it and in fact after a while it will become really obvious. I can now sometimes sex aspidites on the ground in the wild from about a metre away. It is easier to use this method with adults and it is often difficult to do on something like a hatchling children's etc. This method can be tricky with small snakes and snakes that have bold patterns around that area of examination as they often confuse your judgment of thickness.
I find it is also a good idea to view the tail from several angles and directly in front of good lighting. I have had many of my friend's claims that this method is unreliable and should be backed up by probing. I put this to the ultimate test one day and sexed 19 hatchling carpets by visual identification and after my friend double checked with a probe was found to be 100% correct. I have never in the last five years got it wrong and have visually determined the sexes of hundreds of snakes. On occasions I have been unsure with hatchling Antaresia's as they are so small and with these; I suggest the use of a probe. As an obvious way to test your ability to gain this skill, I suggest you visually sex your snake first and then check your result with a probe. With lots of practice you will soon find that you will no longer need to.