You can find a detailed description of the Flea kit here.

This list provides you with some information that can help in the assembly and launch of the Flea

• When cutting fins it is important to make sure that the grain of the wood is parallel to the Leading Edge of the fin.   This is identified in the instructions and on the fin pattern, but warrants pointing out again.
• When cutting, use a straight edge to assure a clean straight line.  Use MANY passes of the knife.  Do NOT try to cut all the way through in one pass.  When cutting WITH the grain, the wood will cut quickly and cleanly.  When cutting the other fin edges, it will take more passes of the knife and result in a slightly more ragged cut.  This can be corrected with sand paper.
• The Flea uses a body tube that is the same diameter as a motor tube.  Meaning that the motor tube and body tube are one in the same.  In this model you must recess the

engine block by pushing it into the model with a  spent motor casing or similar item.  For our educational bulk packs we include a complimentary tube that is used for this purpose (the 2.75" long brown tube)

• Being such a narrow model, it is extra important that the shock cord mount be glued in as flat as possible, flush with the inside surface of the tube.
• The Flea does not make use of an Engine Hook for positive retention of the motor.  Instead you must use what is known as "Friction Fitting" of the motor.  You test fit the motor and if loose (most often), you apply a short wrap of masking tape around the middle of the motor and reinsert.  Repeat until the motor is VERY snug in the rocket.   Lastly, you will notice that fins of the Flea are mounted slight above the   bottom of the rocket.  This provides you with space to place a wrap of masking tape around the end of the motor and the end of the body tube to further secure the motor in place.