Bolt fall-out preventing structure

A bolt fall-out preventing structure comprising:

• a first member to which a first hole is formed, the first hole includes a first portion and a second portion;
• a first bolt member including a first head portion inserted into the first hole of the first member and disposed on the second portion, the first bolt member fixing the first member to a support member;
• a second member to which a second hole is formed, the second hole includes a third portion and a fourth portion, the second member engaging with the first member;
• a second bolt member including a second head portion that opposes the first head portion when the second bolt member is inserted into the second hole of the second member and the first member and the second member are engaged;
• and
• a wall portion on the second head portion of the second bolt member, the wall portion being disposed between a side surface of the first head portion and an inner surface of the second portion.