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The Kiwi and South African defeated Frederik Nielsen from Denmark and local hope Joe Salisbury 7-6 3-6 6-3 6-4 in Thursday's semifinal, in a match that lasted two hours 21 minutes.
In Saturday's final they will take on the American duo of Jack Sock and Mike Bryan, who won their semifinal 6-3 6-1 6-7 7-6 6-4 over Dominic Inglot from Britain and Croatia's Franko Skugor.
Given the five-set epics that Venus and Klaasen had in their last two matches, this victory was more straight forward and although the large crowd on No 1 court were mainly supporting Salisbury and Nielsen, it always felt like being a win for Venus and Klaasen.
"The first set was tight, we saved a break point or two on Raven's serve there, if we'd lost one of those points it could have been a different story," Venus said.
"But we managed to get through that tiebreaker after being up in it a few times, but they kept coming back.
"That really helped us and although they played a great game in the second set to break us, we said to each other that if they can hit four balls like that in a row, that close to the lines, there's nothing we can do.
"So we stuck to our plan, kept working away and tried to find a gap on their games to get a break.
"Raven was returning well and I just needed to help him out a bit, get a few more points and when I made a couple he continued to return well and we got those breaks of serve."
Venus and Sitak had played six tiebreaks in their previous two matches, so it was no surprise that the first set in this match went the same way and it was won by them 8-6.
Klaasen wasn't able to hold serve at 1-2 in the second set and that proved to be the only break in it, levelling the match up at one set apiece.
Nielsen was the guilty party in the third set, getting broken at 3-4 and Venus served out the next game without losing a point to put him and Klaasen one set away from the final.
The veteran Dane was broken again at 3-3 in the fourth and it gave Klaasen and Venus an opportunity to keep holding serve and book a spot in the final, which they happily accepted.
Venus and Klaasen have evolved into the perfect doubles team on court. Klaasen is great at the net, with quick reactions, while Venus can serve bombs and keep the ball deep and hard from the baseline.
"When we spoke in December last year, that's what we thought and how we envisaged us playing," Venus said.
"Raven has got great hands at the net, is very athletic, very fast, makes a lot of returns and then I bring the other element to it, with the power, to set him up.
"It's taken a bit of time for us to really feel like we've got everything in place, we were consistent at the start of the year and knocking on the door of having good results, but never really got over the line.
"But we've kept trusting what we're doing and the process and it seems to be paying off right now."
It will be Venus' third grand slam final in 13 months, having won the men's doubles in last year's French Open and lost in the mixed doubles in the US Open.
Those were magnificent performances, but there is something special about going all the way at Wimbledon.
"It's really exciting," he said.
"It's the one grand slam you look at the most when you're growing up, so to be playing here, in the final and back out on Centre Court, there should be another great atmosphere and I'm really looking forward to the opportunity."