"Doble fondo-vertical" means a double (fence) consisting of a spread (fondo) followed by a vertical or upright (vertical).

A "doble a un tranco" is known as a one-stride double.

"Obstáculo Vertical y de Fondo"
http://www.3caballos.com/disciplinas/salto-obstaculos/obstac...

"al que seguía la ría y en curva el doble (fondo/vertical a un tranco)"
http://www.ecuestreonline.com/espana-segunda-tras-la-primera...

"Double
This is two separate fences positioned with either a one or two non jumping strides in between them, The term "one stride double" refers to the fact that you can fit one non jumping canter stride in between each fence. "
http://www.equestrianandhorse.com/training/jumping.html

"Frank Rothenberger set an appropriately testing 1st round course of 13 fences including: a treble at 5, comprised of a spread then 2 verticals at 1.55m over water ditches; a double of spread and vertical at 9, followed on a related distance by the 4.30m water"
http://www.equestrian.co.uk/ShowJumping/Aachen-Sunday8thJuly...

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Note added at 31 mins (2012-02-07 11:00:54 GMT)
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"He was still taking flyers - he took a double (spread and upright) he launched himself over the first one (85/90cm) and then one massive stride and then launched himself over the second upright and i was just hanging on for dear life lol!!"
http://thepaddocks.proboards.com/index.cgi?board=jumping&act...

"Upright Fence
This is a pole that goes straight across and is at the same height on both of the jump wings. [...]
Spread Fence
This is a single fence that uses two pairs of jump wings so that the fence can be increased in both height and width."
http://www.equestrianandhorse.com/training/jumping.html

"Jumper classes are held over a course of show jumping obstacles, including verticals, spreads, double and triple combinations, usually with many turns and changes of direction."
http://en.wikipedia.org/wiki/Show_jumping