Utensils that are made of many parts that are connected, if it is a strong connection it is prohibited to put it together, if it is always a weak connection it is permissible to make the weak connection.

Chapter 313 Section 7

If a foot of a table brakes you can weakly attach a board so that the table should not break further.

Chapter 313 Section 8

If a foot fell out of a table, you are not allowed to put it back in.