If it's just to keep the wheeled section from moving accidentally by bumping/etc., couldn't you just drill holes in the sides of the frames where the moving table butts up against the stationary table and just use a bolt and nut? Easy enough to remove when the day comes you need to move the table with wheels.
Depending on how tight the fit with the moving table is where it adjoins the stationary one, maybe you would use washers as shims/spacers in between the tables so you aren't' pulling them toward one another in a way that could harm things.
Think this order (described as the bolt would insert from one side to the other): Bolt head, washer (so bolt head is not right against wood when tightening), wood frame for first table, possible washers as spacers, wood frame for second table, washer (so nut will not rub against wood when tightening, nut.
-Dave