center attachment guide for LACK risers

this is for use with LACK enclosure table risers: https://www.thingiverse.com/thing:2545125
it allows you capture the legs in place, but still allow them to be lifted off for full access into the enclosure

10/7/18-added lack center post v4. this part is designed to thread onto the hardware that comes with the lack so if upper raisers are used they are able to centered. print with the flat side down and when installing the opening goes towards the lack table top