These slots are considered skill games and my favorite is the Triple Profits with a hold-spin option.
While fun to play, I prefer Video Poker for better payouts at full-pay machines, however, your skill level has to be higher also.
I have an article at my site about these slots with strategies.
http://www.gamblingteachers.com/online-slots.html
Scroll down the page to Bonus Added Slots Online and then
5) Fruit Machines: familiar in the UK, these games offer interactive fun. There are nudge and hold features permitting the player to either move symbols up or down or hold 1 or more reels for bonus credits. Ex. Fruit Fight & Pub Fruity.
The strategies for Triple Profits is below.
Hope this helps.