Caulk can be one of the most useful tools available to homeowners. The material is easy to apply and will firmly seal gaps and crevices, allowing you to close off drafty areas or prevent water from getting where it shouldn't be.

While you'll likely keep tabs on any caulk in your bathtub or shower, you may be less aware of the caulk around your sinks. If this seal is not in good condition, water can make its way between the sink and the counter, causing damage to your cabinets.

A drop-in sink fits into an opening in a countertop, so the sink rests on top of the countertop. This arrangement can still result in a tiny opening between the sink and the counter, so a layer of caulk is useful to prevent water intrusion. Lee Wallender, writing for the home design site The Spruce, says it's easier for water to spill out of this type of sink since the edge will be slightly raised above the surrounding counter.

Undermount sinks are attached to the underside of the countertop using adhesives or clips. This design can create a more seamless look, but is also more susceptible to leaks. If the sink was not installed properly, or if the sealant has started to pull away, water from the sink can enter gaps between the sink and the underside of the counter.

When caulking a sink, choose a caulk that can stand up to the wet environment. Julie Ryan Evans, writing for Realtor.com, says polyurethane or silicone caulk will both work well since they are waterproof.

Before installing new caulk, remove any old caulk and clean the area around the sink. You may use a caulk remover to soften up the material and make it easier to pull out. A utility knife is a good tool for this process, while needle-nose pliers are helpful for pulling out stubborn pieces.

Some caulk residue will be left over once you've removed the largest pieces. Willow Lane Cabinetry, a company in Hopewell Junction, N.Y., says you should use a rag to apply denatured alcohol to the seam. Renee Miller, writing for SFGate, says you should also scrub the area with soap and water to remove any dirt and debris. Allow the area to dry completely before adding new caulk.

Putting down painter's tape on either side of the seam can be time-consuming, but will also improve the appearance of the caulk line. This step allows you to keep any excess caulk off the sink or countertop.

The nozzles of caulk tubes can be trimmed at different lengths to change the size of the bead you will apply. Start by cutting it at a 45-degree angle at a smaller size, and squeeze some onto a piece of cardboard or paper. Trim the nozzle to release a larger bead if necessary.

Use a caulk gun to apply the bead of caulk around the edge of the sink. Evans says the bead should be applied continuously by moving the gun either away from you or toward you. You can dampen your finger and use it to smooth out the bead, though a putty knife or caulking tool will also work well.

Applying caulk to undermount sinks is more difficult, but you can still do it on your own. Wallender says you'll need to clean out the joint from inside the cabinet, then apply the caulk around the top edge of the sink where it meets the countertop. You may need to repeat this process from the other side.

Remove the painter's tape to take away any excess caulk before it starts to cure. Miller says you can also use a damp cloth or mineral spirits to remove any caulk you may have accidentally gotten on the sink or counter.

Don't use the sink while the caulk is curing. You'll want to wait at least 24 hours, though some caulks may require you to wait longer before they can be exposed to moisture.