There is nothing worse than having a large lead and then losing the game due to a couple of lucky hands by your opponents. It's happened to all of us at one time or another: out of nowhere here come your opponents. First with a lay-down lone, then your team is euchred on what looked like a solid bid. Suddenly a six point lead turns in to a 9-to-9 game and they have the deal. One last set of favorable cards for them and you're left shaking your head and wondering what the heck just happened.
That's how the cards fall at times, and there is nothing you can do to stop it from happening, right? Well, maybe not. What if you had just one more hand to play? How would that have changed your chances of winning? In the hand where they had the lay-down lone, let us suppose that your team had named trump instead of them. It would make no difference whether you made a point or not. The big difference would be that they never were able to play their lone. Now your team would have one more chance to make that final point.
When a team has a significant lead, they should do everything possible to ensure the best chance of winning. This includes naming trump any time when there is possible lone by the opponents that cannot be stopped.
The dealer sits in the West position and has turned up the ten of spades. The score is 9 to 3 in favor of the North/South team. North looks at his hand and, seeing predominantly red cards, orders the ten into the dealer's hand.
As with any donation(AKA block), it is always best to start the hand with a trump lead when possible. In this particular hand, they would have likely made two points anyway. The donation stopped any chance of them making four points
There is one thing to consider before calling a donation: how likely are your opponents to try a lone call? There are players that only call alone when they have an almost perfect hand. In most cases donating to these players will only help them win. The exception would be at scores like 9 to 7 with a jack turned up.