#include <bits/stdc++.h>
using namespace std;
using ll = long long int;
using bigint = int64_t;
const int MOD = 1000000007;
void io_set() {}
void solve() {
  ll n, x, y;
  cin >> n;
  vector<pair<ll, ll> > v;
  vector<char> ans;
  v.push_back({0, 0});
  for (ll i = 0; i < n; i++) {
    cin >> x >> y;
    v.push_back({x, y});
  }
  ll f = 0;
  sort(v.begin(), v.end());
  for (ll i = 1; i <= (int)v.size() - 1; i++) {
    if (v[i].second < v[i - 1].second) {
      f = 1;
      break;
    }
    ll dx = v[i].first - v[i - 1].first;
    for (ll i = 0; i < dx; i++) {
      ans.push_back('R');
    }
    ll dy = v[i].second - v[i - 1].second;
    for (ll i = 0; i < dy; i++) {
      ans.push_back('U');
    }
  }
  if (f) {
    cout << "NO\n";
  } else {
    cout << "YES\n";
    for (auto it : ans) {
      cout << it;
    }
    cout << "\n";
  }
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);
  cout.tie(nullptr);
  ;
  io_set();
  ll tt = 1;
  cin >> tt;
  while (tt--) {
    solve();
  }
  return 0;
}
