"Ricky" wrote
1) I'm getting a new oil furnace in the basement, and the installer
wants to put a brick under each corner. ?? Is this something old-
timers do? Is it a good idea?

Are the bricks to prevent rusting? There has been water in the
basement on several occasions but it only made it to the furnace when
the furnace itself was leaking,

If you had water before, you'll have water again. Maybe next week or next
year or next decade. The bricks buy you a few inches of time. The also
promote good air circulation around it to prevent rusting. In some cases,
it makes it higher, thus easier to service.