I think that's what he means, the bolts that hold the trans to the block.
personally, I never build engines on stands, especially a straight 6. Way too much weight cantilervered out over those tiny wheels, rather unstable. Also, hanging a block by the bell causes significant deflection of the block in the back 1/3. I've actually measured up to 0.002" cylinder distortion in #s 4&5, while the block hung by the bell. I build engines on a wood topped bench, just roll them around for access.