Aragorn tied the knots around his wrists and ankles and around the tree trunks while Frodo positioned his limbs just so, recommending that the ropes be tightened or loosened or the angle changed. Frodo was also the one to remove the many layers of Boromir's clothing once they had him pinned down. Sleeves and leggings had to be left on, but his torso and his groin were quite exposed and became much more so as Frodo skillfully (and gleefully) tongued his nipples and his cock, making Boromir moan.
"That will teach you," Frodo said, "not to treat hobbits like children."
* * *
Frodo removed his own clothes next and straddled Boromir's waist. He leaned close, his erection pressing into Boromir's belly, his bottom inches away from Boromir's straining cock. The Ring on its chain, the only thing Frodo was still wearing, trailed teasingly over Boromir's neck.
If he had his hands free he might take the Ring, or touch Frodo's skin, cup his perfect arse, or even give himself some relief, but as it was he could only writhe and pant.
"That's to teach you," Frodo whispered, "to resist temptation. Just because you see something doesn't mean you'll get it."
* * *
Then Aragorn added his weight, sitting behind Frodo and pulling him up, and both of them gazed down at their repentant captive. Aragorn trailed kisses across Frodo's shoulders and dripped oil over his backside, gently stretching him with one finger and then another. Boromir could not see this clearly, but Frodo's noises of pleasure-pain told him all he needed to know. He longed to be touched that way and no longer teased.
"That's enough," said Frodo, lowering himself over Boromir once again. "I'm ready now."
Aragorn nodded. "You shall learn," he said to Boromir, "to take good care of Frodo."
* * *
But Frodo was not taking good care of Boromir. When Aragorn first plunged into him Frodo yelled (yes) in Boromir's ear, and when the pounding resumed he bit Boromir's neck and held the flesh in his teeth to keep from screaming. Aragorn stroked Frodo's erection in time with his thrusts, and if Boromir weren't trapped and thrashing underneath them it probably would have seemed a very short time before both of them came and Frodo spilled his seed over Boromir's chest, biting hard enough to draw blood.
"And not to take things," said Aragorn, "which do not belong to you."
Merry and Pippin laughed good-naturedly as they released the ropes and set to work on releasing that other tension. Boromir was in such a state that he could spare no thought for pride or shame, and he came in mere seconds, humping against the first thing to come within reach, which happened to be Merry's leg. He heard the hobbits laugh with increasing excitement until they brought each other off as well, all as Boromir drifted in the aftermath of his own climax.
"That'll teach you," said Pippin. "Next time you decide to have an orgy, you'd better invite us!"