Example con Arte de Ascii! (each box is a table, each entry a column)
PK = Primary Key -- FK = Foreign key
can you tell why?

vendor                 
-------------------    
| id [PK] integer |----------\
| name    string  |          |
-------------------          |
                             |
vendoroffer                  |
-----------------------      |
| vendor [FK] integer |<-----/
| plug   [FK] integer |<-----\
| serial      string  |      |
| price       decimal |      |
-----------------------      |
                             |
plug                         |
----------------------       |
| id    [PK] integer |-------/
| motor [FK] integer |----------------------> ...
| gap        float   |
| ...etc?...         |
----------------------