This is the best "glue" for connecting a window and a regulator. Strong but malleable. Because it cures rapidly, make sure you have everything ready, constructed, and lined up. I created my own plunger with a caulking gun, screws, and a spacer, as others have stated. This is an easy project that can be done in less than an hour.
If you don't want to go through the hassle of making your own connector, there are products available from home improvement stores that can be used instead. One option is EZ-Connect's PVC Regulator Connector. It's easy to use and provides a secure connection that will not come apart under pressure.
Another option is J-B Weld. This is a two-part epoxy that can be used for welding metal parts together. Once it has cured, it's almost impossible to remove. You would need a cutting torch or drill to accomplish this task.
The last option is silicone adhesive. This is a soft material that adheres to itself and most other materials. When applied properly, it removes easily without leaving any residue.
There are several types of glues available on the market today that can be used for connecting plastic components. Some examples include Loctite 454, 514, and 601 series sealants. They all work fine but have different characteristics we will discuss below.
The best adhesive is a two-part epoxy that dries quickly, such as Devcon 5 minute epoxy, which is available from Cooksons. To set reliably, it must be well mixed, and I would do it using a plastic coffee stirrer on a square of that rigid transparent wrapping that certain products come in. It's also important to allow enough time for the glue to dry; if you rush this process, you could end up with a partially dried out piece of silver.
There are other options available. Gizmo's World offers acrylic glues for jewelry making purposes. These can be bought as clear liquids that turn into solid colors when applied to objects. They're easy to use and don't smell too bad once they've set. There are several varieties to choose from for different applications; each has its advantages and disadvantages. Acrylic glues are usually less expensive than epoxies, but they may not be as durable over time.
Another option is shellac. This is a natural resin found in some species of tree. When heated, it will flow like syrup and harden when cooled. Like most materials used in craft projects, there are various grades or types of shellac available. The higher quality versions are more brittle and don't stain your fingers when you touch them up after they've been handled by others. Lower quality versions are more flexible and don't stick so well to metals.
Dental-grade resin is the best adhesive, although it might be expensive if you're on a tight budget. Instead of using super glue or crazy glue, consider acrylic resin. It can be costly because it is only meant for use by dentists. This, on the other hand, is the most durable and is intended for dental usage. It's also the least sticky when compared to the others.
Other options include:
Gum arabic - used to stick gems to teeth before they were inserted; still used today in some Middle Eastern countries.
Plastic - used as an alternative to glass beads; doesn't show up on x-rays and doesn't move around in your mouth like ceramic beads do.
Henna - used by some Native Americans to paint designs on their teeth; still available today at some craft stores that sell Indian arts and crafts.
Wax - used to make teeth white before all the fillings came about; no longer recommended due to potential contamination from other materials used in making jewelry.
Beeswax - same as wax, except it's natural and doesn't contain any harmful substances; still used today by some jewelers who prefer its feel over plastic.
Mouth balm - used by some athletes to keep their mouths moist during long practices and games; still used today by rock musicians who need to keep their lips moist.
Rubber cement may be a better choice if you want a liquid mask. I've used it on windows, little spaces, and irregular patches that were too weird to cover, among other things. A sharp edge is required for the adhesive to flow against. Surface tension will cause the glue to flow all the way up to the edge, whether scribed or raised.
The best option by far is paint. There are many colors to choose from, including flat paints for general purposes and enamel paints for decorative effects. Flat paints can be found in any home improvement store and usually cost less than $10 for a gallon. Enamel paints are more expensive but they last forever if taken care of properly. Avoid buying cheapo paint; it's likely to peel off your walls later on.
If you want to save money but don't want to use glue or paint, look into renting space at a community center where they can rent out masks for you to use. This is probably your best bet if you plan to do a lot of masking.