Honestly for solid wood boards (hardwood in your case) just applying wood glue and clamping would provide more than sufficient strength to hold the weight of a cat. Simple glue joints are used to make table tops without additional fasteners. The strength of the glue joint is generally stronger than the wood itself and since your boards have already been machined they provide great gluing surfaces. Just don't clamp so hard you squeeze out all the glue.

20mm (a little more than 3/4") is plenty thick to use most fastening systems including biscuits or dowels. Biscuits you need a special bicuit cutting tool which can be expensive. Dowels benefit from a jig to get them to line up properly. My personal choice is to use pocket screw holes for applications like this. 

A Kreg Mini jig will suffice for your needs as long as you have a power drill and only costs about $13 and you don't need expensive bar clamps as you would with glue alone but a face clamp would benefit to keep everything flush. You can also just use standard quick clamps though. I use mine frequently but there are more advanced models that make positioning easier. I have comparisons of the different Kreg Jig models on my site.

The way I would do it is to drill the pocket screw holes on the undersides of the boards using 3 screws on each side, 1 of which is screwed onto the long board. 2 screws per side would be adequate but I like to have some on the alternate board for glueups like this.



Biscuit, dowel or simple braces for making unit top with inset lid and slim sides?
I use Kubuntu 12.04 with KDE 4.8.3 and wodim / genisoimage 1.1.11, but the problem is on Ubuntu (with Brasero) and occurred in Oneiric as well.

Whenever I try to burn more than 3.8GB (approaching the 4 GB limit) of data onto a DVD, burning fails, aborts, or gives an "error 254."

I have lost more than 50 DVDs this way until I learned about the 3.8GB limit. Anything under 3.8GB burns fine, and DVDs burned with more than 3.8GB have usable data up to 3.8 GB, but then the remaining data is garbled, unaccessible, or the disk is just not recognized.

I'm pretty certain this is related to the replacement of cdrecord / mkisofs with wodim /genioimage (which is a problem that has been described for years). Is there another answer or fix? Re-installing cdrtools/cdrecord/mkisofs in Oneiric and Precise has become a herculean task.  
