You'd need two of those hose pinch pliers, one for each heater hose off the heater core nipples. I've got slightly cheaper hose pinch plastic pliers which are also commonly available in two sizes. The locking slide collar on the plastic ones can't as easily be acidentally opened like threaded lockjaw pliers. Hose pinch pliers have V-shaped or U-shaped jaws so as not to split a rubber hose with a way to keep the jaws shut. Wrapping rags around the hose and using regular locking pliers can also work if you're careful, even two small blocks of wood over the rag and using a shop clamp.

The advantages of using hose pinch pliers in an emergency is it's a quick fix and as long as the hoses don't get damaged and split then you may be able to re-use the existing heater hoses. Even with hose pliers you do risk splitting an old, smaller diameter, thicker walled hose such as these if you try to fully shut off the flow. Also, until the heater core is drained it may continue to drip into the cabin and get under the carpets -so get the hoses off the nipples ASAP at your earliest conveneince and drain the heater core by blowing into the upper nipple. You'll want a pan under the car and lots of old towels. Rinse the firewall area of spilled coolant when done.

This discussion applies to both leaking heater cores and failed heater control valves that can suddenly split, in addition to failed heater hoses, especially an oily/gummy heater hose that can split in the turn below the heater control valve.

My heater core article in the FAQ suggests how to use 1/2" copper plumbing elbows (soldered as a "U") needing two everday hose clamps to bypass the heater core. That's what I started packing after my first 700 heater core failure. Tricky bit there for emergency use is you can't easily disconnect the hoses off the heater core nipples. It will be like they're welded on (the FAQ article discusses this). You then need to pack a good knife and be prepared to sacrifice the hoses. That bypass was meant for the shop when you've got the old heater core disconnected and are waiting for a new one.

Since then I've got a simpler and better emergency kit that I now pack. You don't need to make a bypass, just plug the heater hoses on two sides of the leak, be it the heater core, the valve or a split hose. You need a selection of cheap serrated PVC plumbing plugs that you can get at HDepot (like two 1/2", two 5/8" and one 3/4") plus a couple of suitable hose ring clamps (which are optional if the plugs are a tight fit). If you can get the heater hoses disconnected then great, just plug the open ends (5/8" usually the best fit), otherwise cut the hoses (1/2" then the best fit), with the 3/4" plug for use at the fat bend if it splits and needs to be cut there. Threaded brass or cast iron plumbing plugs will also do if you've got those handy, just more expensive.
--
Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now