A reversal is short stock plus a synthetic-long-stock. Like the conversion it has no directional exposure; its value comes from a small pricing discrepancy and from the interest earned on short sale proceeds.
Reversals are sensitive to two things retail traders underestimate: the cost of borrow in a hard-to-borrow name, and unexpected dividends. Both turn a locked profit into a loss, which is why the desks that run them track borrow rates obsessively.
Example: XYZ at $50.00. Short 100 shares at $50.00, sell the $50 put at $2.15, buy the $50 call at $2.30. You receive $49.85 net and owe $50.00 at expiration — a $15 loss unless interest on the $5,000 short proceeds exceeds it. At 5% for 90 days that interest is about $62, so the package pays.
Related: conversion, put-call-parity, hard-to-borrow, cost-of-carry