Concealed hardware used to join railing and railing components. Comes with 1 pair of steel springs. Can be used inside only. Tools needed to install and not included are a 1" wood drill bit and a No. 2 square bit or screwdriver. Epoxy glue can be used, but is not necessary and is sold separately. Can be used on butt joints and 90 deg. joints. No wood plugs or putty is needed.