You will require the following

1*Face Plate

1* Face Hole Filler

2* Eyes (optional)

additional parts:

2-4*3.2mm X 1.6mm rare earth magnets

2* 6mm airsoft pellets (white, for eyes)

1* Face of choice

Assembly

Take the face plate and put 1-2 magnets in the small holes on both or either side(s). can glue in but use sparingly (you can also attach the face of your choice to the face plate at this time.)

insert the face plate into the face hole filler and put a small drop of glue where you put magnets on the face plate. once done, drop 1 magnet where ever you dropped the glue.

BE CAREFUL NOT TO USE TO MUTCH!

once dry, you can insert the face hole filler into the cavity in Thomas's smoke box (Make sure the eye mechanism within the model is removed). you can glue it in or use a gluestick to hold it in place. it should be a snug but slightly loose fit.

if you haven't yet glued or stuck the face plate to the face of your choice, make sure the holes for the eyes line up correctly.

before you put the face on, put the eyes in the sockets. can use glue tack to help hold them in. but not necessary, the face with magnets should be enough to hold them in.

You're done! make as many faces as you want and easily interchange the faces at your whim without concern of glue tack sticking out.