Open Poser load a Box from the primitives, I colored it blue. Goto Object (upper menu) => Create magnet

The box gets a magnet.
Put the magnet base in the exact middle of the box.

For the magnet set:
xScale and yScale to 150%

For the magnet zone set:

xScale and yScale to 5000%
zScale to 50%

Your box should now look like this:

Poser 1, 2, 3, 4, 5, 7, P8 and PPro2010, P9 and PP2012, P10 and PP2014 Game Dev
"Do not drive faster then your angel can fly"!