Step 1: When a tear is complete it breaches the anorectal wall, the sphincter and the perineal muscles, so the surgeon rebuilds each plane separately with a stitch suited to that tissue.
Step 2: After clearing scar tissue and refreshing the rectal margins, the mucosa and submucosa of the rectum and anus are brought together with vicryl.
Step 3: The muscular layer, the perineal body and levator ani, is reconstructed with catgut, and the superficial tissues are again closed with vicryl, so the repair as a whole relies on both vicryl and catgut.
Step 4: Picking only catgut or only vicryl ignores the layered technique, and silk is rejected outright because being non-absorbable it persists and predisposes to sinus and infection in this contaminated area.
\[\boxed{\text{Vicryl and catgut}}\]