Can men use dildo harnesses? Will she laugh? Does she have to know?
There's no reason why a man can't use a dildo harness. You can easily find a cloth measuring tape. They are sold even at grocery stores. Measure your hips, and use that information to order one that will fit. I personally prefer harnesses made out of nylon webbing since they can be thrown into a washing machine and then dried over a towel rack. They are less bulky than harnesses made out of leather or vinyl, so they fit closer to the body and draw less attention to themselves. They may even be quieter. (I've had a leather harness or two that squeaked when new.)
Also look at the O-ring that will hold the dildo. Can you change it for a ring that is larger or smaller? These rings are readily available at hardware shops in the plumbing section. I keep a bunch on hand in different sizes so I can find a snug fit for the toy of the evening. Some manufacturers sew only one O-ring in place, so you can't switch it for a different size. You may not want to use metal rings. They can cause bruises.
How do you adjust the size of the harness? I prefer Velcro since it is snug and doesn't hurt my hips. But Velcro can be noisy. If you are trying to be stealthy, you may want a harness that adjusts by threading a strap through two rings, or even a buckle. Get the minimum amount of hardware! Thick rings or buckles may bump into your partner's body, and alert him or her to their presence or hurt both of your tender parts.
It's not that difficult to make a harness, if you know how to use a sewing machine (or even sew by hand). Visit a sex shop and look at a few. I prefer a style with a wide waist strap and two more slender straps that go between my legs. It fits kind of like a jock strap. The one-strap style tends to get stuck in my crack, and I don't need the anal abrasion! A harness that just goes around your waist doesn't work very well because the toy is not anchored to your body. It slides around too much, and you don't have good control. Harnesses made out of elastic are sold as “one size fits all,” but they just bounce around and feature even less control. Don't waste your money on such a travesty.
Your penis might get in the way of your harness and toy. Some guys are built so they can just tuck the shaft of their penis inside a hollow dildo. Some toys sold as “penis extenders” will also work in a harness this way. But most guys find that they get pinched if they do this. The base of the dildo can press uncomfortably into the scrotum. Therefore it is common for guys who use dildo harnesses to wear the dildo above their cocks, higher on their hips. This changes the angle of penetration somewhat, but that is fairly easy to get used to.
You don't say why you want to use a dildo harness. So I'm going to mention a few possibilities, for the benefit of the rest of the readers. I've made dildo harnesses for other guys who felt their natural equipment wasn't big enough to satisfy their partners. They wanted something longer and thicker. Guys who were having some problems keeping an erection (or coming too soon) also have asked me for harnesses. Some guys like to use toys, but they want to keep their hands free for other purposes like titplay, body stroking, etc. So they opt for a toy instead of a dildo they will have to use with at least one hand. Some transguys like dildo harnesses because it meets their psychological need to have an erection and penetrate their partners. A harness is dandy to facilitate all of these purposes. And, of course, women love them if they like toys and applying (or receiving) internal pressure and friction.
Buy the right toy for your purpose. Make sure it has a flared base so it will stay put within the ring. Dildos that are too hard can draw attention to themselves. They may not feel natural. The new toys that are made of cyberskin or something similar have a better texture, especially if you have warmed them up in hot water or by keeping them next to your body. Be sure to follow manufacturers' instructions for cleaning and storing the toy so it will be in good shape when you next need it. I personally like toys that have the option of inserting a vibrating bullet. This can add to my fun and also feels good to some partners. But the vibrator does make a noise. Being inside the dildo or a person doesn't eliminate the buzz. If you have a choice, get a longer dildo of the desired thickness. You need the extra length to stay inside your partner, but you will also need to monitor yourself so you don't go in too deep and hurt them.
Why do you want to keep your use of the harness a secret? Are you embarrassed about your reason for using it? Keeping a problem hidden is not a good idea in a relationship. Someone who cares about you will want to know what is going on. Someone who doesn't care about you will be more critical of your sexual performance and more alert to cues that you are not using a biological phallus. I even have some questions about whether it is ethical to fuck somebody with a harness and toy unless they know that is what you are doing, and have consented to play that way. At the very least, you should understand that people do not like to be deceived. The same person who might have agreed to play with toys if this had been discussed beforehand could become quite angry if they find out their mental image of what was happening was not, in fact, the whole story. This is one case where seeking permission IS better than asking for forgiveness. It is easier to get sympathy for facing certain sexual difficulties, and even get help solving that problem, than it is to get a hearing once you are perceived as a dishonest trickster.
If you don't want to tell your partner exactly why you want to use the harness, you can always just say, “This is a fantasy of mine. Let's just try it and see how it feels.” It won't hurt to hint that you have been looking for someone with enough imagination and sense of adventure to approach about using these toys. Promise to take feedback. Use foreplay to get your partner aroused. Put a condom on the toy to help keep it clean, and use lubricant. You don't have to just say, “Are you ready for penetration?” Tease them about being aroused and encourage them to say they want it.
You will need visual contact with the dick to make sure it's still inside, so watch what you are doing, and be prepared to slip out a time or two. Don't make a fuss, just go back in and stroke away. Using a dildo harness can create just enough extra space for your partner to get their hand down there and touch themselves, which helps keep him or her aroused. Ride them into and through the climax, being careful not to go in too deep just because you get aroused. (Secret Hint: If he or she says, “I want more! I want more!” it is okay to go deeper.)
There's no limit on the number of letters per customer, so if you would like to tell me more about your situation, feel free to write again. I might be able to give you more help if I have more information about you.