Keratin glue is the adhesive that is used to attach hair extensions to natural hair. Keratin glue most commonly comes in a small tube or pre-applied to the top of the hair extension. It is also available in a solid stick form, much like a glue stick for a hot glue gun. The stick form of keratin glue is used to apply the glue tip to the hair extension prior to attaching it to the natural hair.

Lay the hair out on a flat surface and gather a 1/4-inch diameter clump in your fingers. Use scissors to cut the hair off of the top fabric. If the hair extensions come in a loose form, then simply gather a 1/4-inch size clump and separate it from the remaining hair.

Trim the top of the hair, using scissors to create a flat top.

Insert a keratin glue stick into the back hole of the keratin glue gun and push it down as far as it will go. Plug the glue gun cord into an electrical outlet and allow the gun to preheat for two to three minutes. You should also plug in the hair extension iron to preheat.

Pick up the clump of hair in one hand and the keratin glue gun in the other hand. Squeeze the trigger on the glue gun to dispense approximately 1/4 tsp. of keratin glue onto the very end of the hair. Use the tip of the glue gun to work the glue all the way around the top 1/4 inch of hair.

Set down the glue gun and pick up the hair extension iron. Squeeze the glued tip of the hair extension between the iron to flatten it and disperse the glue evenly.

Allow the tip to cool and then cut any uneven hairs at the top using scissors.

Lift up the top part of your hair around the crown and secure it with a clip so that it is out of your way. You only need to secure the uppermost layer of hair which will hang on top of the hair extensions to hide them.

Gather a clump of natural hair that is approximately 1/4 inch in diameter. Rotate the hair one or two times near the scalp. Insert a hair shield around the clump of natural hair and push it as close to the scalp as possible.

Place the glued tip of the hair extension under of the clump of hair and position it so that it is approximately 1/4 inch away from the scalp.

Place the hair extension iron around both the natural hair and the hair extension and press down for two to three seconds to bond the extension to the natural hair. Set the iron aside.

Twist the bonded area in between your fingers to smooth out the glue.