What is the maximum depth for anal penetration? How long of a probe can I use? So far, I have been using different handles and tools I can find around the house.
The depth of the rectum, the first section of the large intestine, differs a great deal from one individual to another. But I would guesstimate that anything over eight inches long could be a problem. You may be able to go deeper if you have a flexible device that can be coaxed around a corner. (Once you are past the rectum, the bowel takes a sharp turn, across the stomach.) Be aware, however, that the lining of the bowel is extremely thin and fragile. A puncture, even a tiny one, can allow fecal matter to leak. This will cause peritonitis, a potentially fatal infection of the lining of the abdominal cavity. You may not see enough blood to warn you to head for the emergency room. So if you suddenly develop a high fever or a rigid belly and pain after high-risk anal play, call an ambulance.
You can make anal penetration with toys safer if you use a thick, greasy lubricant like Crisco or Elbow Grease. (You can't use oil-based lubricants during anal fucking with a penis, however, because it may damage the condom, which you are of course using.) Putting a condom on your ten-inches-or-less toys will make it easier to keep them free from bacterial buildup. Wash them well after use with hot water and soap. Don't put anything sharp or breakable in your butt, and don't put anything up there that could slip in and get lost. Use something with a base that is too big to go into your ass. Otherwise, you'll need to see a doctor to have the object retrieved. Bottles are popular objects for anal play during masturbation, which is a dangerous and sad thing, because an open bottle can form a vapor lock in there and become impossible to remove without sedation and even surgery.
Please consider buying some of the really wonderful silicone toys that were made for anal penetration. You can keep them in a locked toolbox along with your lube and condoms if you are worried about being found out. They can be kept very clean by boiling them after use. (See the manufacturer's directions for more information.) You'll be a lot safer and you'll also have more fun because dildos and butt plugs were made specifically for prostate-tickling and ass-stuffing.