ARLINGTON HEIGHTS – How is it that Chris Block, one of the best-known trainers at Arlington, and a trainer whose Chicago starters always seem to take betting action, can be producing a positive return on investment in so many areas?Take a look at a horse named Triple Check, one of seven – and part of a Block-trained coupled entry with Gold Former – in the featured fourth race Saturday. Triple Check hasn’t raced since last October at Keeneland, and Racing Form trainer stats say that’s a good thing, since Block has connected with eight of his last 18 long-term comeback runners, generating a return on investment of $3.26. The fourth-race feature, for second-level Illinois-bred allowance horses, is carded for one mile on grass, and despite his notoriety as a turf trainer, Block’s last 198 grass runners have produced a $2.33 return. Route races like Saturday’s fourth? That’s another good one: a return of $2.41 from a large sample size of 291 runners. And finally allowance races, where $2 bets on Block’s last 100 starters would have brought $2.16 back into the bankroll. The concern with Triple Check might be distance, since Saturday’s one-mile trip seems to be on the short side of optimal. But Triple Check made his last three starts in open allowance-race competition, and facing Illinois-breds, he may be able to rally in time even at a distance shorter than his best. If not, Block-trained Gold Former could come out on top. Two for 2 to start his career, Gold Former already has scored a one-mile grass win at the Arlington meet, rallying to beat first-level Illinois-breds on May 6. Full Flame and Roi le Roi appear to have the best chance if a Block horse doesn’t prevail.The featured fourth is one of three allowance races on the program along with race 9, an open race for entry-level allowance runners on turf, and race 10, an Illinois-bred first-level Polytrack race. Bill’s Presence might be a tepid favorite in the ninth, but while often close, she rarely wins. Consider front-running Delightful Daisy, who fell apart late in a last-start comeback after being forced into a frenetic early pace.After showing ability over the winter at Fair Grounds, Lumberyard Jack has disappointed in his two most recent starts, but he could rebound in the nightcap, which is carded for one and one-eighth miles on the main track. If not Lumberyard Jack, then maybe Fast Albert, who exits a creditable fourth-place finish facing much stronger foes in an open second-level allowance on May 20.