Female tails are usually half as thick a quarter of the tail's length from the base. While learning, look at adult snakes of known sex before trying it on juveniles and adults of unknown sex. Male boa constrictors have spurs on either side of the vent that are significantly larger than those of the females. Breeding Boas requires closely copying their natural conditions. This includes a seasonal day night light cycle, winter cooling, misting, and many other factors.
Timing is crucial.
Although captive breeding is encouraged, it requires more dedication than simply keeping a few snakes. The General Care and Maintenance of Red Tailed Boas. This is part of The Herpetocultural Library published by Advanced Vivarium Systems. Reproductive Husbandry of Pythons and Boas. Institute for Herpetelogical Research, Stanford.