Adding a table leaf on Shabbat

Hi,

One may add a leaf to a table on Shabbat.

Although one may not create a roof over a space on Shabbat, this is acceptable 1) because one is adding to an existing "roof", 2) because the table is made for such expansion, and 3) because the primary problem is where there are both roof and walls, and our tables do not have walls.

(Rivivot Ephraim 1:222:3)

Have a great day,
Mordechai