On the Original Grapple Rule
"As they outnumber their opponent so heavily it is likely that they will try to over-power him rather than kill, so each hit they score will be counted as attempts to grapple the Hero"
Two of the 5 orcs that can attack hit.
"Two of the Orcs have grappled the Hero, and if his score with 4 dice is less than their score with 2 dice he has been pinned helplessly."
This is the fighter's Hit Dice (as indicated by the level title "Hero") versus the total of the hit dice of the creatures who successfully hit.
"If it is a tie they are struggling, with the Hero still on his feet, but he will be unable to defend himself with his weapon. If the Hero scores higher than the Orcs use the positive difference to throw off his attackers, i.e. the Hero scores 15 and the Orcs scored but 8, so the Hero has tossed both aside, stunning them for 7 turns between them."
It is unsaid, of course, that if the Orcs win, the Hero is captured. Obviously the level of success indicates the rounds of stunning divided among all participants.
This example includes a common technique that I use, of not dicing for monster hit points, till the monster is struck.
Grappling: Attack as normal, without weapons. The successful attackers and defender both roll a combined number of d6's equal to their Hit Dice.
On a tie, both parties struggle, neither able to take action.
If the defender wins, he throws off all the successful attackers. They are stunned for a round. He may take his action as normal.
If the attackers win, the defender is pinned and helpless.
And some optional modifiers:
Advanced Option 1: The difference between the defenders winning roll and the attackers losing roll is the number of rounds of stunning that may be divided among the defenders.
Advanced Option 2: Once overpowered, the defender may try to escape using half his hit dice, versus the hit dice of the creatures restraining him. On a loss he takes the difference as subdual damage.