Wood picture frame moulding can break because of age or accident. Repairs to the moulding can be quite simple or require some time and effort, depending on the extent of the damage. Nevertheless, broken picture frame mouldings can be repaired at home with only a few tools.
Pry the corners apart with a screwdriver so there is enough space between the two pieces of wood to drip glue onto the two sections. Do this by inserting the end of the screwdriver between the two sections of wood at the corner of the frame and pushing the handle down. It is not necessary to completely separate the two pieces of wood at the corner.
Drip or pour wood glue onto both pieces of wood on either side of the corner.
Tap the two pieces of wood back together using a hammer. In most wooden picture frames, there are metal connectors inside the wood pieces at the corners, and with a light tapping on the wood, they will go back together. The glue is necessary, however, to make sure they stay together.
Fasten the corners together using a clamp so they will stay in place. Tighten the clamp just tight enough for the corners and frame to stay in place, but not so tight the clamp makes indentations in the wood.
Remove any excess glue from the wood using a cloth and allow the glue to dry.
Apply wood putty to the broken area as smoothly as possible and allow the putty to dry.
Sand down the dried wood putty, using a fine-grain sandpaper, between 150 and 180 grit.
Stain the frame with a wood stain and paintbrush. You can select a stain colour that closely matches the original picture frame stain, but if it has been a long time since the frame has been stained, the stain will not match the colour of the wood. Therefore, you will need to stain the entire frame for the colour to be even.