Large knobs should be made from replacement plywood just like replacement pieces, except that the stub on the piece where the knob has broken off must be cut cleanly by your scroll saw before tracing hole; the newly cut and fitted knob is then glued onto the smooth cut and piece inserted into puzzle. Insert toothpicks to increase pressure of new knob against stub and allow dry overnight.
Small knobs may be replaced with plastic wood.
Keep the platform of broken and uneven plies to maximize purchase area for the plastic wood.
Examine neck of receiving keyhole for broken knob to consider widening with Dremel tool to reduce chance of future break.
Trim and clean where top paper damaged.
Cut strips of Release Paper to outline missing part of piece.
Leave purchase area without release paper as this is connection point.
Bend strip of release paper to match shape of hole to be outlined. Insert using tweezers making sure strip fits snugly against adjacent piece and any corners.
Insert drop of Elmers Wood Glue onto part of the puzzle piece you are building onto (the purchase area) using awl or small screwdriver.
Pack plastic wood into missing area surrounded by the Purchase Area and the release paper with small screwdriver, filling above the puzzle level and firmly tamping down with small screwdriver. (Like a dentist filling a large cavity)
Fix many such knobs at one time and let dry overnight.
When dry, before separating, carefully rub back of two pieces with file to remove excess plastic wood; then loosen pieces from each other using awl against bottom of new knob as you push it up and out.
Peel away release paper with tweezers, using a rotating motion with your wrist.
Level the top of the repair with the Dremel tool and cutter bit #9901 or #9902. Leave new knob in adjacent piece as you grind down excess plastic wood close to puzzle level. Then, separate pieces and finish grinding down excess plastic wood to puzzle level. Always grind toward purchase area of new knob.
Use needle file to roughen and level top. Check height of repair, file or grind as needed.
Use X-acto knife to cut off any fuzzy plastic wood fibers along top edge of new knob. Use needle files to smooth edges and fit knob properly into adjacent piece.
If knob is too low or too uneven or very thin at the neck or weakened, grind down a little more and glue watercolor paper onto knob as in Par. VI.A. extending across break onto solid stub of piece knob broke off of. This frequently happens when replacing a small knob that has broken off entirely.
If knob has been repapered, cut away excess paper with X-acto knife. You can also compensate for knobs which dont quite fill the hole by leaving a little more paper as you cut away the excess.
Color as in Par. VI.B.
The back of the puzzle only needs to be repaired if the hole is more than 1 ply deep or the missing bottom ply is so extensive that the piece can wobble. Follow instructions above.