"Terry" wrote in message
...
The vents holes under my sister's house are one cinder block square.

The cheap vent covers were nailed in place by just driving nails into
the mortar joints. Her dogs push them out to get under her house.

My solution will be to just take some one inch thick wood and cut the
pieces the same size as the cinder block and wedge them around the
opening and screw the vents to the wood.

Any better solutions?

There are vent covers that have little spring loaded hooks on the back that
hold tightly to brick holes or grates. You might check hardware stores for
those. No tools needed, but they might have to be adapted to cinder block
vents, as they work best with 1 inch mesh grating vents.
Roger