Round Table

Setting aside, for the moment, the Round Table exhibited in the Great Hall of the castle at Winchester, England, the mythical Round Table was supposed to have been created for Uthur Pendragon by Merlin.
From Uthur it passed to King Leodegrance, aagin possibly through Merlin's arrangement. He, Malory says, sought to fill its seats (or seiges) but wars and other losses meant that the most he ever appears to have managed was 100 out of the 150 vacant seats.
Then Arthur received the Table as a wedding gift from Leodegrance when he married Leodegrance's daughter, Guinevere and over time filled the remaining seats, up till the Quest for the Grail, after which, the accounts make clear, the Table was enevr again filled

Practicality

At a size of 150 seats, the table would have been unfeasibly large, but with any fewer there would have been a risk that storytellers would have had to enforce a discrimination between classes of Arthurian knights, as to whether or no they were sufficiently valiant to emrit the Round Table. With 150, no-one could be expected to remember when the literary limit had been reached.
The Winchester Table (which reaches 18 feet in diameter(!)) has 24 places around its circumference, each inscribed with the name of its tenant.

Of these several are well-known Arthurian knights:

• Sir Galahad
• Sir Lancelot du Lac
• Sir Gawain
• Sir Percival
• Sir Tristram de Lyones
• Sir Gareth
• Sir Bedevere
• Sir Palomedes
• Sir Lamorak
• Sir Bors
• Sir Pelleas
• Sir Kay
• Sir Ector
• Sir Mordred

Others are perhaps slightly more obscure:

• Sir Brunour
• Sir Digore
• Sir Dagonet -- otherwise known as Arthur's court fool (but then, looking at *some* modern day knights ... )
• Sir Lionell
• Sir Bleoberis
• Sir Lucan

And some require a little deciphering:

• "Sir Lacotemale Tayle" is La Cote Mail Taile, the Ill-Dressed Knight, which is another name for Sir Brunour, something perhaps unknown to the painter of the Table.
• "Sir Lybyus Dysconys" is Le Bel Desconneu, the Beautiful Unknown, or Gawain's son, Guinglain.

And some seem otherwise unknown to modern eyes:

• Sir Safer (see discussion page)
• Sir Alynore or Alymere