[charlesdm]

You borrow against your stock, of course, so you don't have to realise the capital gain yet get access to the cash. If you're worried about downside protection, you can always buy a put option for the stock you pledged at its current value.

[sowbug]

Many publicly traded companies prohibit their employees from buying puts or selling calls on their stock, as it misaligns incentives, similarly to how shorting the stock causes you to benefit from a decline in price.