Moore and Smalley Palace Shield Premier Division
In a match reduced to 38 overs per team at the Riverside, it was Thornton who batted first.
They made 119-9 from their reduced allocation of overs, largely thanks to a knock of 47 from opening batsmen Jon Eade.
He was one of only three batters to reach double figures with fellow opener Joe McMillan (12) and Jordan Beech (20 not out) the others.
Eade was one of four wickets for Michael Walling, who ended with figures of4-31 from 11 overs.
Ian Walling claimed 3-28 from 15 overs with Andy Booker (1-17) also collecting a wicket.
In reply, Garstang were relatively untroubled in reaching their target with 10 overs in hand.
Openers Michael Walling and Allan Cook got them off to a good start, laying the platform for their eventual victory.
Michael Walling had reached 32 before he was dismissed, LBW to David Crawforth, which brought Mark Walling to the crease.
He added 25 but was unable to be there at the finishing line as he was bowled by Jordan Beech.
Cook was undefeated on 46 as Garstang secured victory with a reply of 120-2, Tom Wells their other unbeaten batsman with a single to his name.
Beech took 1-24 and Crawforth 1-14 as Garstang claimed 11 points.
That leaves them third in the table with 114 points, one adrift of second-placed Fulwood and Broughton.
The first team have a double header this weekend as they travel to Torrisholme on Saturday before facing Eccleston the following day.