forms the isolation joint pocket in this preferred embodiment the form is constructed from a plastic wood pressed wood or manufactured wood that is not significantly affected by water or concrete each side 20 of the form 10 is made from two pieces that are hinged 90 in the center the center hinge s allow the sides 22 of the form to be collapsed inward to pull them away from the poured and set concrete that is poured around the form hinge s 30 are placed on the corners of the form that operate with the center hinges 90 to collapse the form into the concrete poured around the isolation joint hardware such as screws or other similar fastening means 32 secure the hinges to the form when the sides of the form are straightened a rod 40 is placed through u201c u u201d clips 42 that keep the sides of the form in an essentially straight configuration the rods maintain the sides straight as the concrete is poured around the form and pushed in on the sides of the form another typical method of maintaining the sides of the form in a straight condition is fill the inside of the form with an expendable material such as sand or other material that is removed from.