St Mirren kept their play-off hopes alive in the Ladbrokes Championship with a hard-fought 1-0 home win over Dumbarton.The Saints had to be patient and poised to make home advantage tell. Rocco Quinn fed Lawrence Shankland, whose shot was superbly blocked by Mark Brown.At the other end, Frazer Wright's header was scooped off the line by Jamie Langfield.The second half was also a tight affair until David Clarkson squeezed a pass through to Shankland, who powered into the into the far corner with conviction.A second nearly followed immediately as Clarkson missed an achievable volley at the back post, but Alex Rae's men had done enough.